Abstract: The Yangtze River, Huaihe River and Xin'anjiang River witnessed heavy flood simultaneously during Meiyu period in 2020. It's rarely happened in history. The Chuhe River Basin is a tributary basin to Yangtze River Basin, which witnessed the flood exceeded altering water level. The water level above Xianghekou Sluice in upstream has exceeded the historical highest water level. The Huangcao Twice Dike and Huangcao Third Dike applied to store water the fifth time in history. This paper mainly uses the reservoir's storage flow process reverse estimated by changes of reservoir storage and the inter dike flow process reverse estimated by the generalized triangles of each dike water storage capacity, combined stage-discharge relationship curve,analyzes the effects of the large reservoir's dispatching, the medium reservoir's storage and the application of Huangcao Twice Dike and Huangcao Third Dike in reducing the peak and water lever of flood peak. The corresponding station's water level reduced about 0.5~1.5 meters, which effectively mitigated the flood prevention pressure of the downstream reach.