diff --git a/install/23-Sub2API.sh b/install/23-Sub2API.sh
index 7cc5e3b..cd46542 100644
--- a/install/23-Sub2API.sh
+++ b/install/23-Sub2API.sh
@@ -10,14 +10,24 @@ port80=8230
 install_dir=/root/data/docker_data/Sub2API
 update_script="$install_dir/auto-update.sh"
 
-# 交互：选择安装或仅执行 Docker 更新
+# 交互：已有安装时默认只更新，避免覆盖数据库账号、密码和连接配置
+existing_install=0
+if [ -f "$install_dir/docker-compose.yml" ]; then
+    existing_install=1
+fi
+
 echo "请选择操作："
-echo "  1) 安装 Sub2API（默认）"
-echo "  2) 不安装，立即执行 Docker 更新"
+if [ "$existing_install" -eq 1 ]; then
+    echo "  1) 已安装，仅更新 Sub2API app 镜像（默认，安全，不覆盖配置/数据库）"
+    echo "  2) 强制重装 Sub2API（危险，会重写 docker-compose.yml）"
+else
+    echo "  1) 安装 Sub2API（默认）"
+    echo "  2) 不安装，立即执行 Docker 更新"
+fi
 read -r -p "请输入选项 [1/2]（默认 1）：" action_choice
 action_choice="${action_choice:-1}"
 
-if [ "$action_choice" = "2" ]; then
+if { [ "$existing_install" -eq 1 ] && [ "$action_choice" = "1" ]; } || { [ "$existing_install" -eq 0 ] && [ "$action_choice" = "2" ]; }; then
     echo "已选择：立即执行 Docker 更新。"
     if [ -x "$update_script" ]; then
         "$update_script"
@@ -43,6 +53,16 @@ if [ "$action_choice" = "2" ]; then
     exit 0
 fi
 
+if [ "$existing_install" -eq 1 ] && [ "$action_choice" = "2" ]; then
+    echo "检测到已有 Sub2API 安装：$install_dir/docker-compose.yml"
+    echo "强制重装会覆盖 docker-compose.yml，可能导致数据库账号、密码或连接配置被重置。"
+    read -r -p "如确需重装，请输入 REINSTALL 确认：" reinstall_confirm
+    if [ "$reinstall_confirm" != "REINSTALL" ]; then
+        echo "未确认强制重装，已退出。原有配置未修改。"
+        exit 0
+    fi
+fi
+
 
 # 1、更新包（更新失败不阻断后续安装）
 export DEBIAN_FRONTEND=noninteractive