Abstract: On September 7-8, 2023, extreme heavy rainfall that exceeded the historical record occurred in Shenzhen, breaking 7 historical extremes since 1952, the year of meteorological records in Shenzhen. By investigating and analyzing the rain and water conditions and disaster situation of the "9·7" extreme heavy rainstorm in Shenzhen, use the monitoring data from the rainfall stations of the Shenzhen Municipal Water Affairs Bureau and the Meteorological Bureau.Using HydroMPM (HydroMulti-processes Modeling) modeling cloud platform to establish one- and two-dimensional mathematical numerical models of flooding, to review the "9·7" extreme rainstorm process in Shenzhen in 2023, and to analyze the causes of flooding, identify the existing flood control and drainage engineering system weaknesses, put forward the planning and design, engineering system, watershed management, intelligent water, universal participation and other planning measures, providing a basis for revealing the causes of flood and waterlogging disasters in high-density urban watersheds and proposing prevention and control countermeasures.