Abstract: Influenced by strong convection, a heavy rainfall occurred in Yi-Shu-Si River from August 13 to 14, 2020, which led to the largest flood in Yihe River since 1960, and the largest flood in Shuhe River since 1974. Based on the flood information data, the paper analyzes the cause, process, characteristics and return period of flood. The return period of flood peak of Linyi station in Yihe River and Daguanzhuang station in Shuhe River after reduction are 15 years and 22 years respectively. As well as, this paper summarizes the highlights of the dispatching decision.