diff --git a/backend/src/index.js b/backend/src/index.js
index f1f0bc7..5220d8c 100644
--- a/backend/src/index.js
+++ b/backend/src/index.js
@@ -4,6 +4,7 @@ const authRoutes = require('./routes/auth');
 const fileRoutes = require('./routes/files');
 const shareRoutes = require('./routes/share');
 const syncRoutes = require('./routes/sync');
+const errorHandler = require('./middleware/errorHandler');
 
 const app = express();
 const PORT = process.env.PORT || 3000;
@@ -17,6 +18,9 @@ app.use('/api/files', fileRoutes);
 app.use('/api/share', shareRoutes);
 app.use('/api/sync', syncRoutes);
 
+// Error handler
+app.use(errorHandler);
+
 // Health check
 app.get('/api/health', (req, res) => {
   res.json({ status: 'ok' });
diff --git a/backend/src/middleware/errorHandler.js b/backend/src/middleware/errorHandler.js
new file mode 100644
index 0000000..f3df715
--- /dev/null
+++ b/backend/src/middleware/errorHandler.js
@@ -0,0 +1,57 @@
+// 统一错误处理中间件
+const errorHandler = (err, req, res, next) => {
+  console.error('Error:', err);
+
+  // JWT 错误
+  if (err.name === 'JsonWebTokenError') {
+    return res.status(401).json({
+      success: false,
+      error: 'Invalid token',
+      code: 'INVALID_TOKEN'
+    });
+  }
+
+  if (err.name === 'TokenExpiredError') {
+    return res.status(401).json({
+      success: false,
+      error: 'Token expired',
+      code: 'TOKEN_EXPIRED'
+    });
+  }
+
+  // Multer 文件上传错误
+  if (err.code === 'LIMIT_FILE_SIZE') {
+    return res.status(400).json({
+      success: false,
+      error: 'File too large',
+      code: 'FILE_TOO_LARGE'
+    });
+  }
+
+  if (err.code === 'LIMIT_FILE_COUNT') {
+    return res.status(400).json({
+      success: false,
+      error: 'Too many files',
+      code: 'TOO_MANY_FILES'
+    });
+  }
+
+  // 数据库错误
+  if (err.code === 'SQLITE_CONSTRAINT') {
+    return res.status(400).json({
+      success: false,
+      error: 'Data constraint violation',
+      code: 'CONSTRAINT_VIOLATION'
+    });
+  }
+
+  // 默认错误
+  const statusCode = err.statusCode || 500;
+  res.status(statusCode).json({
+    success: false,
+    error: err.message || 'Internal server error',
+    code: err.code || 'INTERNAL_ERROR'
+  });
+};
+
+module.exports = errorHandler;