Abstract: In 2020,Qiantang River Basin in Zhejiang Province experienced the second longest plum rain season since 1949,leading to severe floods over the Xin'anjiang Reservoir.Maximum flood and the highest water level occurred in the Xin'anjiang Reservoir since its first impoundment of 61 years ago, its nine spillways were fully opened for the first time.Zhejiang Province implemented precise reservoir regulation and successfully prevented basin severe flood.Based on this, the flood review and risk simulation of "20200707" flood were systematically carried out, the basin flood control risk affected by the cumulative effect of plum rain flood was analyzed, and the weakness of flood control system in the Qiantang River basin was evaluated.The results show that the Qiantang River Basin still has the risk of a 100-year basin severe flood, and the Xin'anjiang Reservoir area, Lanjiang River and Hangzhou City downstream of Fuchun River still have the flood risk.This paper proposes several comprehensive management measures, such as building an integrated basin flood control engineering system from the source to the estuary, researching the function adjustment of the Xin'anjiang Reservoir, and increasing the flood control capacity of large and medium-sized reservoirs in the basin.The research results can provide a reference for improving the flood control level of the Qiantang River Basin.