diff --git a/backend/flask_app.py b/backend/flask_app.py
index d6377ba..443eaf7 100644
--- a/backend/flask_app.py
+++ b/backend/flask_app.py
@@ -1,12 +1,18 @@
 from datetime import date, datetime
 from pathlib import Path
 import os
+import sys
 import json
 import shutil
 import sqlite3  # 保留用于数据迁移
 import logging
 import mysql.connector
 
+# 确保 backend 目录在 sys.path 中（兼容 gunicorn --preload 模式）
+_backend_dir = os.path.dirname(os.path.abspath(__file__))
+if _backend_dir not in sys.path:
+    sys.path.insert(0, _backend_dir)
+
 from flask import Flask, jsonify, render_template, request, send_file, session, redirect
 from werkzeug.security import generate_password_hash, check_password_hash