Abstract: This study monitors rainfall runoff events in a subway depot in Beijing, and based on event mean concentration (EMC) and cumulative pollutant quality-cumulative runoff curve (M (v) curve), The results showed that there were significant differences in the concentrations of suspended solids (SS), chemical oxygen demand (COD), ammonia nitrogen (NH₄⁺-N) and total phosphorus (TP) in runoff of different underlying surfaces of subway car depot (p<0.05). The initial erosion intensity of the drainage area dominated by building roof was stronger than that dominated by track. Based on SWMM model, the parameters and spatial distribution of rainwater storage tank in the study area were adjusted, and further analysis showed that the decentralized design of rainwater storage tank could further reduce the drainage volume and improve the water quality of the drainage and storage tank, thus reducing the treatment difficulty and cost of rainwater reuse. The research results can provide reference for optimizing the design of stormwater storage tank and improving the control and utilization of stormwater.