Abstract: Catchment area is an important input parameter in the process of urban storm water model modeling, which has an important impact on the simulation accuracy of urban stormwater model. Under multiple measured rainstorm scenarios, the study on the impact to the SWMM model overflow simulation results of three catchment zoningmethods including drainage pipe network-based, terrain data-based, and combining terrain and pipe network data, has been carried out. The results show that: compared with other catchment zoing methods, the sub-catchment results obtained by the combining terrain data and pipe network as catchment zoning method are most consistent with the real scenario. And its overflow simulation accuracy is about 6.29% higher than that of the drainage pipe network-based catchment zoning method, indicating that it is more suitable for urban storm flood simulation.