diff --git a/modules/i18n_messages/api_auth.py b/modules/i18n_messages/api_auth.py
index c73c259a..3eef9728 100644
--- a/modules/i18n_messages/api_auth.py
+++ b/modules/i18n_messages/api_auth.py
@@ -37,6 +37,10 @@ MESSAGES = {
         "zh-CN": "未登录",
         "en-US": "Not logged in",
     },
+    "auth.session_expired": {
+        "zh-CN": "登录状态已过期，请重新登录",
+        "en-US": "Your login session has expired. Please log in again.",
+    },
     "auth.host_mode_tutorial_not_applicable": {
         "zh-CN": "宿主机模式无需设置新手教程状态",
         "en-US": "Tutorial status does not apply in host mode",
diff --git a/server/app_legacy.py b/server/app_legacy.py
index eb71229e..5ff5bdf1 100644
--- a/server/app_legacy.py
+++ b/server/app_legacy.py
@@ -821,7 +821,7 @@ def api_login_required(view_func):
     @wraps(view_func)
     def wrapped(*args, **kwargs):
         if not is_logged_in():
-            return jsonify({"error": "Unauthorized"}), 401
+            return jsonify({"error": tr("auth.session_expired")}), 401
         return view_func(*args, **kwargs)
 
     return wrapped
diff --git a/server/auth_helpers.py b/server/auth_helpers.py
index acb5b5d7..2daddbf0 100644
--- a/server/auth_helpers.py
+++ b/server/auth_helpers.py
@@ -34,7 +34,7 @@ def api_login_required(view_func):
     @wraps(view_func)
     def wrapped(*args, **kwargs):
         if not is_logged_in():
-            return jsonify({"error": "Unauthorized"}), 401
+            return jsonify({"error": tr("auth.session_expired")}), 401
         return view_func(*args, **kwargs)
     return wrapped