Abstract: Taking the“25·7”rainstorm flood process as the research object, integrating multi-source monitoring data and hydrological simulation outputs to systematically analyze the rainfall characteristics, flood response, and and reservoir scheduling benefits of the Miyun Reservoir Basin.The findings indicate that the rainstorm exhibited characteristics of prolonged duration, concentrated rainfall areas, and intense short-term precipitation; small and medium basins showed concentrated flood peaks with short lag times, while large basins demonstrated significant flood storage capacity; the Miyun Reservoir received approximately 1.024 billion m³ of flood inflow, with the Baihe River contributing nearly 50%；the combined effect of floods from multiple basins resulted in a "double-peak" inflow pattern for the Miyun Reservoir; the reservoir achieved a peak reduction rate of 82.9% and a flood retention rate of 72.3%, effectively mitigating the downstream flood accumulation risk. These results can serve as a reference for optimizing flood regulation strategies in mountainous basins under extreme rainstorm scenarios.