diff --git a/apps/em/cd.py b/apps/em/cd.py
index 76eb04fc..15d2ae45 100644
--- a/apps/em/cd.py
+++ b/apps/em/cd.py
@@ -17,7 +17,7 @@ def get_tyy_data(*args):
             resp = sc.recv(1024)
             if not resp:
                 raise ParseError("采集器返回空数据")
-            if len(resp) < 8:
+            elif len(resp) < 8:
                 raise ParseError("设备未启动")
             json_data = resp[5:-4]
             json_str = json_data.decode('utf-8')