diff --git a/shouji/main.py b/shouji/main.py
index 7522a56..0d4103b 100644
--- a/shouji/main.py
+++ b/shouji/main.py
@@ -306,6 +306,21 @@ class BtSerial:
     def total_tx(self) -> int:
         return self._total_bytes_tx
 
+    def is_connected(self) -> bool:
+        """检测手机是否连上 — 用缓存值 + CD 信号, 不阻塞"""
+        if not self.ser or not self.ser.is_open:
+            return False
+        if self._phone_connected:
+            return True
+        # 尝试 CD (Carrier Detect) — 蓝牙SPP连接时此信号会拉高
+        try:
+            if self.ser.cd:
+                self._phone_connected = True
+                return True
+        except Exception:
+            pass
+        return self._phone_connected
+
     def _read_loop(self):
         """后台读线程 — 非阻塞轮询"""
         buf = b""
@@ -321,9 +336,7 @@ class BtSerial:
                     self._total_bytes_rx += len(chunk)
                     self._last_data_time = time.time()
 
-                    if not self._phone_connected:
-                        self._phone_connected = True
-                        self._log("*** 手机已连接 ***")
+                    self._phone_connected = True
 
                     # 按已知协议标记对齐数据
                     while True:
@@ -349,7 +362,6 @@ class BtSerial:
                 if self._phone_connected and \
                    (time.time() - self._last_data_time) > 30:
                     self._phone_connected = False
-                    self._log("*** 手机已断开 ***")
 
                 time.sleep(0.05)
             except OSError:
@@ -443,9 +455,19 @@ class MobileService:
         self._poll_thread = None
 
     def _poll_loop(self):
-        """后台轮询 — 处理收数据 + 自动响应握手/控制码"""
+        """后台轮询 — 处理收数据 + 自动响应握手/控制码 + 连接状态检测"""
+        prev_phone_connected = False
         while self.serial and self.serial.running:
             try:
+                # ── 连接状态检测 (通过 CD 信号 + 数据接收) ──
+                conn = self.serial.is_connected()
+                if conn and not prev_phone_connected:
+                    self._log("*** 手机已连接! ***")
+                    prev_phone_connected = True
+                elif not conn and prev_phone_connected:
+                    self._log("*** 手机已断开 ***")
+                    prev_phone_connected = False
+
                 data = self.serial.read_all()
                 if data:
                     responses, _ = self.proto.feed(data)