Abstract: On July 20,2021,extreme rainstorm occurred in Zhengzhou,resulting in serious flood disaster. In this paper, the rainstorm conditions in Zhengzhou are transplanted to Shenzhen and Beijing respectively, and the urban flood simulation model is used to simulate in order to sum up the experiences and lessons and analyze the causes of this disaster.The simulation analysis results show that had the extreme rainstorm occurred in Shenzhen or Beijing, it would have produced serious flood disasters, river overflow and serious ponding.The single practice of improving the urban flood control and drainage standard through engineering measures can deal with the rainfall within the design standard, but cannot deal with the extreme rainstorm events exceeding the design standard. Therefore,it is suggested to carry out joint drainage,joint commissioning and overall management of urban flood and waterlogging at the river basin, regional and urban levels; Simulate the urban waterlogging and ponding risk under different rainfall conditions, especially the exceeding standard rainstorm,predict and evaluate the urban disaster bearing capacity,formulate and improve early warning indicators and flood control management emergency response plan, improve the government's comprehensive coordination ability,timely issue early warning and prompt information before the rainstorm, and quickly guide relevant departments and citizens to take necessary preventive measures, protect the life safety of citizens and reduce property losses.