Abstract: In view of the frequent occurrence of flood disasters in the river basin and the business demand of flood disasters prevention in the Pi River Basin of HuaiHe tributary,this paper researched on the joint dispatching of flood prevention of reservoir groups based on the flood prevention task of four mixed reservoirs in Fo,Mo,Bai, Xiang. This paper established and solved the model of flood prevention dispatching, which the object of joint flood prevention dispatching was the minimum total flood prevention capacity of reservoir group in Pi River Basin. On the premise of ensuring the safety of reservoir project and controlling section lower than the guaranteed flow rate, this paper researched joint flood prevention dispatching by taking the floods in June and July 2020 as an example. The flood storage capacity of each flood in June could be reduced to 39.96 million m³,the July flooding can effectively reduce the maximum flow at controlled cross section based on optimizing dispatching, which greatly reduced flood risk and provided support for flood prevention safety in the Pi River Basin.