diff --git a/src/main/java/com/ycwl/basic/pricing/service/impl/CouponServiceImpl.java b/src/main/java/com/ycwl/basic/pricing/service/impl/CouponServiceImpl.java
index 1130f302..31f8b74d 100644
--- a/src/main/java/com/ycwl/basic/pricing/service/impl/CouponServiceImpl.java
+++ b/src/main/java/com/ycwl/basic/pricing/service/impl/CouponServiceImpl.java
@@ -70,17 +70,27 @@ public class CouponServiceImpl implements ICouponService {
         if (!isCouponApplicable(coupon, products, totalAmount)) {
             return BigDecimal.ZERO;
         }
-        
+
+        // 计算适用商品的总价
+        BigDecimal applicableProductsTotal = calculateApplicableProductsTotal(coupon, products);
+
         BigDecimal discount;
         if (coupon.getCouponType() == CouponType.PERCENTAGE) {
-            discount = totalAmount.multiply(coupon.getDiscountValue().divide(BigDecimal.valueOf(100), 4, RoundingMode.HALF_UP));
+            // 百分比优惠券基于适用商品总价计算,而非购物车总价
+            discount = applicableProductsTotal.multiply(coupon.getDiscountValue().divide(BigDecimal.valueOf(100), 4, RoundingMode.HALF_UP));
             if (coupon.getMaxDiscount() != null && discount.compareTo(coupon.getMaxDiscount()) > 0) {
                 discount = coupon.getMaxDiscount();
             }
         } else {
+            // 固定金额优惠券
             discount = coupon.getDiscountValue();
         }
-        
+
+        // 限制优惠金额不超过适用商品总价,防止优惠溢出到其他SKU
+        if (discount.compareTo(applicableProductsTotal) > 0) {
+            discount = applicableProductsTotal;
+        }
+
         return discount.setScale(2, RoundingMode.HALF_UP);
     }
     
@@ -128,7 +138,37 @@ public class CouponServiceImpl implements ICouponService {
             return false;
         }
     }
-    
+
+    /**
+     * 计算适用商品的总价
+     * @param coupon 优惠券配置
+     * @param products 商品列表
+     * @return 适用商品的总价
+     */
+    private BigDecimal calculateApplicableProductsTotal(PriceCouponConfig coupon, List<ProductItem> products) {
+        // 如果优惠券没有商品类型限制,返回所有商品总价
+        if (coupon.getApplicableProducts() == null || coupon.getApplicableProducts().isEmpty()) {
+            return products.stream()
+                    .map(ProductItem::getSubtotal)
+                    .reduce(BigDecimal.ZERO, BigDecimal::add);
+        }
+
+        try {
+            // 解析适用商品类型列表
+            List<String> applicableProductTypes = objectMapper.readValue(
+                    coupon.getApplicableProducts(), new TypeReference<List<String>>() {});
+
+            // 计算适用商品的总价
+            return products.stream()
+                    .filter(product -> applicableProductTypes.contains(product.getProductType().getCode()))
+                    .map(ProductItem::getSubtotal)
+                    .reduce(BigDecimal.ZERO, BigDecimal::add);
+        } catch (Exception e) {
+            log.error("解析适用商品类型失败", e);
+            return BigDecimal.ZERO;
+        }
+    }
+
     @Override
     @Transactional
     public CouponUseResult useCoupon(CouponUseRequest request) {
diff --git a/src/test/java/com/ycwl/basic/pricing/service/CouponOverflowTest.java b/src/test/java/com/ycwl/basic/pricing/service/CouponOverflowTest.java
new file mode 100644
index 00000000..8b840a83
--- /dev/null
+++ b/src/test/java/com/ycwl/basic/pricing/service/CouponOverflowTest.java
@@ -0,0 +1,325 @@
+package com.ycwl.basic.pricing.service;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.ycwl.basic.pricing.dto.ProductItem;
+import com.ycwl.basic.pricing.entity.PriceCouponConfig;
+import com.ycwl.basic.pricing.enums.CouponType;
+import com.ycwl.basic.pricing.enums.ProductType;
+import com.ycwl.basic.pricing.service.impl.CouponServiceImpl;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * 优惠券溢出问题测试
+ * 测试多SKU场景下优惠券优惠金额不会溢出到不适用的商品
+ */
+@ExtendWith(MockitoExtension.class)
+@DisplayName("优惠券溢出问题测试")
+class CouponOverflowTest {
+
+    @InjectMocks
+    private CouponServiceImpl couponService;
+
+    @Mock
+    private ObjectMapper objectMapper;
+
+    @BeforeEach
+    void setUp() {
+        // 使用真实的ObjectMapper,避免mock导致的问题
+        couponService = new CouponServiceImpl(null, null, new ObjectMapper());
+    }
+
+    @Test
+    @DisplayName("固定金额优惠券 - 多SKU场景优惠金额超过适用商品总价应被截断")
+    void testFixedAmountCoupon_MultiSKU_DiscountExceedsApplicableTotal() {
+        // 准备商品列表: PHOTO_PRINT(10元) + PHOTO_PRINT_MU(3元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("10.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("3.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("13.00");
+
+        // 优惠券配置: 满0减5元,仅适用于PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("5.00"),
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为3元(适用商品总价),而非5元
+        assertTrue(discount.compareTo(new BigDecimal("3.00")) == 0, "优惠金额应被截断为适用商品总价");
+    }
+
+    @Test
+    @DisplayName("固定金额优惠券 - 优惠金额小于适用商品总价应正常优惠")
+    void testFixedAmountCoupon_MultiSKU_DiscountWithinApplicableTotal() {
+        // 准备商品列表: PHOTO_PRINT(10元) + PHOTO_PRINT_MU(8元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("10.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("8.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("18.00");
+
+        // 优惠券配置: 满0减5元,仅适用于PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("5.00"),
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为5元(配置值)
+        assertTrue(discount.compareTo(new BigDecimal("5.00")) == 0, "优惠金额未超过适用商品总价,应为配置值");
+    }
+
+    @Test
+    @DisplayName("百分比优惠券 - 应基于适用商品总价计算而非购物车总价")
+    void testPercentageCoupon_MultiSKU_CalculateOnApplicableTotal() {
+        // 准备商品列表: PHOTO_PRINT(100元) + PHOTO_PRINT_MU(50元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("100.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("50.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("150.00");
+
+        // 优惠券配置: 9折,仅适用于PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.PERCENTAGE,
+                new BigDecimal("10.00"),  // 10% off = 9折
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为5元(50 * 10% = 5),而非15元(150 * 10% = 15)
+        assertTrue(discount.compareTo(new BigDecimal("5.00")) == 0, "百分比优惠应基于适用商品总价计算");
+    }
+
+    @Test
+    @DisplayName("百分比优惠券 - 计算结果超过适用商品总价应被截断")
+    void testPercentageCoupon_MultiSKU_DiscountExceedsApplicableTotal() {
+        // 准备商品列表: PHOTO_PRINT(100元) + PHOTO_PRINT_MU(3元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("100.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("3.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("103.00");
+
+        // 优惠券配置: 5折,仅适用于PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.PERCENTAGE,
+                new BigDecimal("50.00"),  // 50% off = 5折
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 理论优惠1.5元(3 * 50% = 1.5),实际不应超过3元
+        assertTrue(discount.compareTo(new BigDecimal("3.00")) <= 0, "优惠金额不应超过适用商品总价");
+    }
+
+    @Test
+    @DisplayName("无商品类型限制的优惠券 - 应用于所有商品")
+    void testCoupon_NoProductTypeRestriction() {
+        // 准备商品列表: PHOTO_PRINT(10元) + PHOTO_PRINT_MU(8元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("10.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("8.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("18.00");
+
+        // 优惠券配置: 满0减5元,无商品类型限制
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("5.00"),
+                BigDecimal.ZERO,
+                null  // 无商品类型限制
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为5元
+        assertTrue(discount.compareTo(new BigDecimal("5.00")) == 0, "无商品类型限制时应应用于所有商品");
+    }
+
+    @Test
+    @DisplayName("无商品类型限制的优惠券 - 优惠金额超过总价应被截断")
+    void testCoupon_NoProductTypeRestriction_ExceedsTotalPrice() {
+        // 准备商品列表: PHOTO_PRINT(2元) + PHOTO_PRINT_MU(1元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("2.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("1.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("3.00");
+
+        // 优惠券配置: 满0减10元,无商品类型限制
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("10.00"),
+                BigDecimal.ZERO,
+                null
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应被截断为3元
+        assertTrue(discount.compareTo(new BigDecimal("3.00")) == 0, "优惠金额应被截断为商品总价");
+    }
+
+    @Test
+    @DisplayName("多商品类型限制的优惠券 - 计算多个适用商品的总价")
+    void testCoupon_MultipleProductTypeRestriction() {
+        // 准备商品列表: PHOTO_PRINT(10元) + PHOTO_PRINT_MU(8元) + VLOG_VIDEO(20元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("10.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("8.00")),
+                createProductItem(ProductType.VLOG_VIDEO, new BigDecimal("20.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("38.00");
+
+        // 优惠券配置: 满0减10元,适用于PHOTO_PRINT和PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("10.00"),
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT\",\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为10元(适用商品总价18元,优惠10元未超限)
+        assertTrue(discount.compareTo(new BigDecimal("10.00")) == 0, "多商品类型限制时应正确计算适用商品总价");
+    }
+
+    @Test
+    @DisplayName("边界情况 - 适用商品总价为0")
+    void testCoupon_ApplicableTotalIsZero() {
+        // 准备商品列表: 仅有PHOTO_PRINT(10元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("10.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("10.00");
+
+        // 优惠券配置: 满0减5元,仅适用于PHOTO_PRINT_MU(购物车中无此商品)
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("5.00"),
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为0(适用商品总价为0,自动截断)
+        assertTrue(new BigDecimal("0.00").compareTo(discount) == 0, "适用商品总价为0时优惠金额应为0");
+    }
+
+    @Test
+    @DisplayName("边界情况 - 优惠金额刚好等于适用商品总价")
+    void testCoupon_DiscountEqualsApplicableTotal() {
+        // 准备商品列表: PHOTO_PRINT(10元) + PHOTO_PRINT_MU(5元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("10.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("5.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("15.00");
+
+        // 优惠券配置: 满0减5元,仅适用于PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.FIXED_AMOUNT,
+                new BigDecimal("5.00"),
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 优惠金额应为5元
+        assertTrue(discount.compareTo(new BigDecimal("5.00")) == 0, "优惠金额刚好等于适用商品总价时应正常优惠");
+    }
+
+    @Test
+    @DisplayName("百分比优惠券 - 带最大优惠金额限制且超过适用商品总价")
+    void testPercentageCoupon_WithMaxDiscount_ExceedsApplicableTotal() {
+        // 准备商品列表: PHOTO_PRINT(100元) + PHOTO_PRINT_MU(3元)
+        List<ProductItem> products = Arrays.asList(
+                createProductItem(ProductType.PHOTO_PRINT, new BigDecimal("100.00")),
+                createProductItem(ProductType.PHOTO_PRINT_MU, new BigDecimal("3.00"))
+        );
+        BigDecimal totalAmount = new BigDecimal("103.00");
+
+        // 优惠券配置: 5折,最大优惠10元,仅适用于PHOTO_PRINT_MU
+        PriceCouponConfig coupon = createCoupon(
+                CouponType.PERCENTAGE,
+                new BigDecimal("50.00"),
+                BigDecimal.ZERO,
+                "[\"PHOTO_PRINT_MU\"]"
+        );
+        coupon.setMaxDiscount(new BigDecimal("10.00"));
+
+        // 执行计算
+        BigDecimal discount = couponService.calculateCouponDiscount(coupon, products, totalAmount);
+
+        // 验证: 理论优惠1.5元(3 * 50%),不受最大优惠10元限制,但仍不超过适用商品总价3元
+        assertTrue(discount.compareTo(new BigDecimal("3.00")) <= 0, "优惠金额不应超过适用商品总价");
+        assertTrue(discount.compareTo(new BigDecimal("1.50")) >= 0, "优惠金额应为计算值1.5元");
+    }
+
+    // ========== 辅助方法 ==========
+
+    /**
+     * 创建商品项
+     */
+    private ProductItem createProductItem(ProductType productType, BigDecimal subtotal) {
+        ProductItem item = new ProductItem();
+        item.setProductType(productType);
+        item.setSubtotal(subtotal);
+        item.setQuantity(1);
+        item.setUnitPrice(subtotal);
+        return item;
+    }
+
+    /**
+     * 创建优惠券配置
+     */
+    private PriceCouponConfig createCoupon(CouponType type, BigDecimal value,
+                                          BigDecimal minAmount, String applicableProducts) {
+        PriceCouponConfig coupon = new PriceCouponConfig();
+        coupon.setId(1L);
+        coupon.setCouponName("测试优惠券");
+        coupon.setCouponType(type);
+        coupon.setDiscountValue(value);
+        coupon.setMinAmount(minAmount);
+        coupon.setApplicableProducts(applicableProducts);
+        coupon.setIsActive(true);
+        return coupon;
+    }
+}