diff --git a/vnpy/trader/ui/mainwindow.py b/vnpy/trader/ui/mainwindow.py
index 4eba1f33..94abc4cc 100644
--- a/vnpy/trader/ui/mainwindow.py
+++ b/vnpy/trader/ui/mainwindow.py
@@ -55,7 +55,7 @@ class MainWindow(QtWidgets.QMainWindow):
 
     def init_dock(self):
         """"""
-        self.trading_widget, trading_dock = self.create_dock(
+        trading_widget, trading_dock = self.create_dock(
             TradingWidget, "交易", QtCore.Qt.LeftDockWidgetArea
         )
         tick_widget, tick_dock = self.create_dock(