In response to the problem of low modeling efficiency caused by complex drainage network structure in urban flood modeling, a drainage network generalization method combining hydrological analysis and rainwater inlets was proposed by comprehensively considering factors such as urban hydrological characteristics, pipeline diameter, drainage flow direction, and distribution of main roads, and applied in Huangpu District, Guangzhou City . This method transfers the inflow from the rainwater inlet connected to the drainage branch pipe to the main pipe network node of the corresponding drainage zone for confluence calculation, which helps rapid modeling of urban flood. Based on the coupled hydrodynamic model of surface runoff and underground pipe flow, the flood process simulated by models constructed using this method, the current drainage network