diff --git a/services/cache.py b/services/cache.py
index 913705b..30b6225 100644
--- a/services/cache.py
+++ b/services/cache.py
@@ -5,6 +5,7 @@
 提供素材下载缓存功能，避免相同素材重复下载。
 """
 
+import json
 import os
 import hashlib
 import logging
@@ -14,6 +15,8 @@ import uuid
 from typing import Optional, Tuple
 from urllib.parse import urlparse, unquote
 
+import psutil
+
 from services import storage
 
 logger = logging.getLogger(__name__)
@@ -62,6 +65,7 @@ class MaterialCache:
 
     LOCK_TIMEOUT_SEC = 30.0
     LOCK_POLL_INTERVAL_SEC = 0.1
+    LOCK_STALE_SECONDS = 24 * 60 * 60
 
     def __init__(self, cache_dir: str, enabled: bool = True, max_size_gb: float = 0):
         """
@@ -100,6 +104,96 @@ class MaterialCache:
         assert self.cache_dir
         return os.path.join(self.cache_dir, f"{cache_key}.lock")
 
+    def _write_lock_metadata(self, lock_fd: int, lock_path: str) -> bool:
+        """写入锁元数据，失败则清理锁文件"""
+        try:
+            try:
+                process_start_time = psutil.Process(os.getpid()).create_time()
+            except Exception as e:
+                process_start_time = None
+                logger.warning(f"Cache lock process start time error: {e}")
+            metadata = {
+                'pid': os.getpid(),
+                'process_start_time': process_start_time,
+                'created_at': time.time()
+            }
+            with os.fdopen(lock_fd, 'w', encoding='utf-8') as lock_file:
+                json.dump(metadata, lock_file)
+            return True
+        except Exception as e:
+            try:
+                os.close(lock_fd)
+            except Exception:
+                pass
+            self._remove_lock_file(lock_path, f"write metadata failed: {e}")
+            return False
+
+    def _read_lock_metadata(self, lock_path: str) -> Optional[dict]:
+        """读取锁元数据，失败返回 None（兼容历史空锁文件）"""
+        try:
+            with open(lock_path, 'r', encoding='utf-8') as lock_file:
+                data = json.load(lock_file)
+            return data if isinstance(data, dict) else None
+        except Exception:
+            return None
+
+    def _is_process_alive(self, pid: int, expected_start_time: Optional[float]) -> bool:
+        """判断进程是否存活并校验启动时间（防止 PID 复用）"""
+        try:
+            process = psutil.Process(pid)
+            if expected_start_time is None:
+                return process.is_running()
+            actual_start_time = process.create_time()
+            return abs(actual_start_time - expected_start_time) < 1.0
+        except psutil.NoSuchProcess:
+            return False
+        except Exception as e:
+            logger.warning(f"Cache lock process check error: {e}")
+            return True
+
+    def _is_lock_stale(self, lock_path: str) -> bool:
+        """判断锁是否过期（进程已退出或超过最大存活时长）"""
+        if not os.path.exists(lock_path):
+            return False
+        now = time.time()
+        metadata = self._read_lock_metadata(lock_path)
+        if metadata:
+            created_at = metadata.get('created_at')
+            if isinstance(created_at, (int, float)) and now - created_at > self.LOCK_STALE_SECONDS:
+                return True
+            pid = metadata.get('pid')
+            pid_value = int(pid) if isinstance(pid, int) or (isinstance(pid, str) and pid.isdigit()) else None
+            expected_start_time = metadata.get('process_start_time')
+            expected_start_time_value = (
+                expected_start_time if isinstance(expected_start_time, (int, float)) else None
+            )
+            if pid_value is not None and not self._is_process_alive(pid_value, expected_start_time_value):
+                return True
+            return self._is_lock_stale_by_mtime(lock_path, now)
+        return self._is_lock_stale_by_mtime(lock_path, now)
+
+    def _is_lock_stale_by_mtime(self, lock_path: str, now: float) -> bool:
+        """基于文件时间判断锁是否过期"""
+        try:
+            mtime = os.path.getmtime(lock_path)
+            return now - mtime > self.LOCK_STALE_SECONDS
+        except Exception as e:
+            logger.warning(f"Cache lock stat error: {e}")
+            return False
+
+    def _remove_lock_file(self, lock_path: str, reason: str = "") -> bool:
+        """删除锁文件"""
+        try:
+            os.remove(lock_path)
+            if reason:
+                logger.info(f"Cache lock removed: {lock_path} ({reason})")
+            return True
+        except FileNotFoundError:
+            return True
+        except Exception as e:
+            logger.warning(f"Cache lock remove error: {e}")
+            return False
+
     def _acquire_lock(self, cache_key: str) -> Optional[str]:
         """获取缓存锁（跨进程安全）"""
         if not self.enabled:
@@ -111,9 +205,14 @@ class MaterialCache:
         while True:
             try:
                 fd = os.open(lock_path, os.O_CREAT | os.O_EXCL | os.O_WRONLY)
-                os.close(fd)
+                if not self._write_lock_metadata(fd, lock_path):
+                    return None
                 return lock_path
             except FileExistsError:
+                if self._is_lock_stale(lock_path):
+                    removed = self._remove_lock_file(lock_path, "stale lock")
+                    if removed:
+                        continue
                 if time.monotonic() >= deadline:
                     logger.warning(f"Cache lock timeout: {lock_path}")
                     return None
@@ -126,12 +225,7 @@ class MaterialCache:
         """释放缓存锁"""
         if not lock_path:
             return
-        try:
-            os.remove(lock_path)
-        except FileNotFoundError:
-            return
-        except Exception as e:
-            logger.warning(f"Cache lock release error: {e}")
+        self._remove_lock_file(lock_path)
 
     def is_cached(self, url: str) -> Tuple[bool, str]:
         """
@@ -357,9 +451,12 @@ class MaterialCache:
                 cache_key = os.path.splitext(filename)[0]
                 lock_path = self._get_lock_path(cache_key)
                 if os.path.exists(lock_path):
-                    # 该文件正在被其他任务使用，跳过删除
-                    logger.debug(f"Cache cleanup: skipping locked file {filename}")
-                    continue
+                    if self._is_lock_stale(lock_path):
+                        self._remove_lock_file(lock_path, "cleanup stale lock")
+                    else:
+                        # 该文件正在被其他任务使用，跳过删除
+                        logger.debug(f"Cache cleanup: skipping locked file {filename}")
+                        continue
                 try:
                     os.remove(file_info['path'])
                     total_size -= file_info['size']