Abstract:[Purposes] To investigate the spatial distribution of runoff under heavy rainfall scenarios in Chengkou County, Chongqing Municipality, and to provide reference for regional disaster prevention and mitigation. [Methods] The SCS model was improved, coupled with soil and land use data, to simulate the runoff volume under six scenarios of 24-hour rainfall ranging from 50 to 250 mm, to analyze the distribution of runoff in townships under the land use changes in 2010 and 2020, and to select four representative heavy rainfall events for spatial simulation of runoff volume. [Findings]The total amount of runoff in Chengkou County is significantly positively correlated with rainfall, and the higher the rainfall, the faster the runoff increases with the increase in the number of runoff curves, and the increase in flood risk is obvious; under the same rainfall intensity, the high-grade area of the total amount of runoff is mainly distributed in the southwestern townships of the study area; the increase in the grassland makes the simulated runoff grades decrease, and the increase in the unutilized land does not have a significant impact on runoff grades, and the changes in rainfall runoff is closely related to the changes in land use; four representative heavy rainfalls were selected for the spatial simulations of runoff volume. Land use changes are closely related to rainfall runoff changes; the results of four actual rainfall simulations show that the townships of Shuanghe, Zhouxi, Mingtong, Gecheng, Xiuqi, Heyu and Dong"an in the study area are the key preventive areas for heavy rainfall and flooding. [Conclusions] The research results can provide support for heavy rainfall and flood disaster forecasting and early warning in Chengkou County.