There is no available drainage pipe network data in many urban areas affecting the accuracy of urban flood simulations. Therefore, a new method is needed to characterize the drainage capacity of the networks. We used the equivalent infiltration approach (RIA) of rainwater wells and the equivalent infiltration approach on road only (CIR) in the simulations of high-resolution urban flood model. With Xixian New District as the research area, the urban flood process was simulated and then compared with the measured data. According to the results of flooding under actual rainfall and designed rainfall conditions, it is found that the method can accurately characterize the drainage capacity of the pipe networks and improve the accuracy of the model compared to the original simulation method.