In order to study the influence of different parameters on SWMM simulation results in urban rainwater simulation, the SWMM hydrological model of Guangzhou Tianhe Wisdom City was constructed. Simultaneous monitoring of rainfall runoff water quality and water quantity was carried out in the study area. The model parameters were determined and verified, and the sensitivity of hydrological and hydraulic parameters and water quality parameters were analyzed based on the Morris method. The results show that the maximum infiltration rate in hydrological and hydraulic parameters is the most sensitive to the total runoff volume, and the surface Manning coefficient is the most sensitive to runoff peak. The infiltration parameter is the main parameter affecting hydrological hydraulic simulation results. The exponent in water quality parameters is the most sensitive to pollutant simulation results. The sensitivity of the antecedent dry days to the simulation results of pollutants is higher than that of runoff flow simulation.