用qtdesigner创建两个窗口，在主窗口里面放置一个按钮，用pyuic解析为py文件。

主窗口文件名one.py，二级窗口文件名main_window_v1.py。 

import sys
import one
import main_window_v1
from PyQt5.QtWidgets import *class SecondWindow(QMainWindow, main_window_v1.Ui_MainWindow):def __init__(self):super(SecondWindow, self).__init__()self.setupUi(self)def open(self):second.show()class MainWindow(QMainWindow, one.Ui_Form):def __init__(self):super(MainWindow, self).__init__()self.setupUi(self)self.pushButton.clicked.connect(SecondWindow.open)if __name__ == "__main__":app = QApplication(sys.argv)win = MainWindow()second = SecondWindow()win.show()sys.exit(app.exec_())

参考：

PyQt5 + qtdesigner 多窗口设计/多页面显示_qtdesigner设计多窗口-CSDN博客

PyQt5-打开新窗口（多窗口）_哔哩哔哩_bilibili