diff --git a/padsleep.py b/padsleep.py
index c588ea7..217b989 100644
--- a/padsleep.py
+++ b/padsleep.py
@@ -232,10 +232,9 @@ class AdbManager:
             return []
 
     def get_ready_device(self) -> str | None:
-        """返回第一个已连接设备的串号，无则返回 None。"""
-        for d in self.list_devices():
-            if d["status"] == "device":
-                return d["serial"]
+        """返回当前已连接设备的串号，无则返回 None。"""
+        if self._device is not None:
+            return self._device.serial
         return None
 
     def is_ready(self) -> bool: