diff --git a/backend/services/data-management-service/src/main/java/com/datamate/datamanagement/application/KnowledgeItemApplicationService.java b/backend/services/data-management-service/src/main/java/com/datamate/datamanagement/application/KnowledgeItemApplicationService.java
index 9d53c89..23dfebe 100644
--- a/backend/services/data-management-service/src/main/java/com/datamate/datamanagement/application/KnowledgeItemApplicationService.java
+++ b/backend/services/data-management-service/src/main/java/com/datamate/datamanagement/application/KnowledgeItemApplicationService.java
@@ -27,12 +27,13 @@ import com.datamate.datamanagement.interfaces.dto.ImportKnowledgeItemsRequest;
 import com.datamate.datamanagement.interfaces.dto.KnowledgeItemPagingQuery;
 import com.datamate.datamanagement.interfaces.dto.KnowledgeItemResponse;
 import com.datamate.datamanagement.interfaces.dto.UpdateKnowledgeItemRequest;
-import com.fasterxml.jackson.databind.ObjectMapper;
 import jakarta.servlet.http.HttpServletResponse;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.apache.commons.collections4.CollectionUtils;
 import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.compress.archivers.zip.ZipArchiveEntry;
+import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream;
 import org.springframework.http.HttpHeaders;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -46,8 +47,10 @@ import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.format.DateTimeFormatter;
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 import java.util.UUID;
@@ -63,8 +66,9 @@ public class KnowledgeItemApplicationService {
     private static final Set<String> SUPPORTED_TEXT_EXTENSIONS = Set.of("txt", "md", "markdown");
     private static final DateTimeFormatter EXPORT_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
     private static final String EXPORT_FILE_PREFIX = "knowledge_set_";
-    private static final String EXPORT_FILE_SUFFIX = ".json";
-    private static final String EXPORT_CONTENT_TYPE = "application/json";
+    private static final String EXPORT_FILE_SUFFIX = ".zip";
+    private static final String EXPORT_CONTENT_TYPE = "application/zip";
+    private static final int MAX_FILE_BASE_LENGTH = 120;
 
     private final KnowledgeItemRepository knowledgeItemRepository;
     private final KnowledgeSetRepository knowledgeSetRepository;
@@ -228,16 +232,25 @@ public class KnowledgeItemApplicationService {
         BusinessAssert.notNull(response, CommonErrorCode.PARAM_ERROR);
         KnowledgeSet knowledgeSet = requireKnowledgeSet(setId);
         List<KnowledgeItem> items = knowledgeItemRepository.findAllBySetId(setId);
-        List<KnowledgeItemResponse> responses = KnowledgeConverter.INSTANCE.convertItemResponses(items);
 
         response.setContentType(EXPORT_CONTENT_TYPE);
         response.setCharacterEncoding(StandardCharsets.UTF_8.name());
         response.setHeader(HttpHeaders.CONTENT_DISPOSITION,
             "attachment; filename=\"" + buildExportFileName(knowledgeSet.getId()) + "\"");
 
-        ObjectMapper objectMapper = new ObjectMapper();
-        try {
-            objectMapper.writeValue(response.getOutputStream(), responses);
+        try (ZipArchiveOutputStream zos = new ZipArchiveOutputStream(response.getOutputStream())) {
+            zos.setEncoding(StandardCharsets.UTF_8.name());
+            Map<String, Integer> nameCounter = new HashMap<>();
+            for (KnowledgeItem item : items) {
+                String entryName = buildItemEntryName(item, nameCounter);
+                ZipArchiveEntry entry = new ZipArchiveEntry(entryName);
+                zos.putArchiveEntry(entry);
+                byte[] contentBytes = (item.getContent() == null ? "" : item.getContent())
+                    .getBytes(StandardCharsets.UTF_8);
+                zos.write(contentBytes);
+                zos.closeArchiveEntry();
+            }
+            zos.finish();
         } catch (IOException e) {
             log.error("export knowledge items error, setId: {}", setId, e);
             throw BusinessException.of(SystemErrorCode.FILE_SYSTEM_ERROR);
@@ -254,6 +267,50 @@ public class KnowledgeItemApplicationService {
         return EXPORT_FILE_PREFIX + setId + "_" + LocalDateTime.now().format(EXPORT_TIME_FORMATTER) + EXPORT_FILE_SUFFIX;
     }
 
+    private String buildItemEntryName(KnowledgeItem item, Map<String, Integer> nameCounter) {
+        String rawTitle = StringUtils.isNotBlank(item.getTitle()) ? item.getTitle() : "item-" + item.getId();
+        String baseName = sanitizeFileName(rawTitle);
+        if (StringUtils.isBlank(baseName)) {
+            baseName = "item-" + item.getId();
+        }
+        baseName = trimToLength(baseName, MAX_FILE_BASE_LENGTH);
+
+        String extension = item.getContentType() == KnowledgeContentType.MARKDOWN ? "md" : "txt";
+        String baseKey = baseName + "." + extension;
+        int count = nameCounter.getOrDefault(baseKey, 0);
+        nameCounter.put(baseKey, count + 1);
+        if (count == 0) {
+            return baseKey;
+        }
+        return buildIndexedFileName(baseName, extension, count);
+    }
+
+    private String buildIndexedFileName(String baseName, String extension, int index) {
+        String suffix = "_" + index;
+        int maxBaseLength = Math.max(1, MAX_FILE_BASE_LENGTH - suffix.length());
+        String safeBase = trimToLength(baseName, maxBaseLength);
+        return safeBase + suffix + "." + extension;
+    }
+
+    private String sanitizeFileName(String name) {
+        if (name == null) {
+            return "";
+        }
+        String normalized = name.replaceAll("[\\\\/:*?\"<>|]", "_");
+        normalized = normalized.replaceAll("\\s+", " ").trim();
+        return normalized;
+    }
+
+    private String trimToLength(String value, int maxLength) {
+        if (value == null) {
+            return "";
+        }
+        if (value.length() <= maxLength) {
+            return value;
+        }
+        return value.substring(0, maxLength);
+    }
+
     private KnowledgeContentType resolveContentType(DatasetFile datasetFile) {
         String extension = getFileExtension(datasetFile);
         if (StringUtils.isBlank(extension)) {