With the continuous progress of urbanization, the problems of flood and waterlogging in urban become worsening. The SWMM model widely used at home and abroad plays an important role in flood control and drainage.The determination of model parameter is the key issue of reliable application.The paper used Morris screening method and took the central urban area of Longyan city as example to analyze the effect degree of different hydrological and hydraulic parameters in SWMM model on regional peak flow and runoff coefficient. The results show that the parameters of the greatest impact on runoff coefficient are impervious surface coverage, minimum penetration rate and overflow width, and that on flow of flood peak is impervious surface coverage, ragged coefficient of permeability and overflow width. The result can help improve the selection efficiency of model parameters, upgrade the accuracy of simulation result and provide reference for the application research of SWMM model.