Abstract: In view of the change of inflow flood rule of the Three Gorges Reservoir caused by the regulation and storage of Xiluodu and Xiangjiaba cascade reservoirs during the operation period, which leads to the unreasonable design flood limit water level, the study of seasonal flood limit water level of Three Gorges Reservoir is carried out. Firstly, the discharge process of Xiangjiaba Reservoir is obtained according to the dispatching rules of Xiluodu and Xiangjiaba Reservoirs. Then, the multi-dimensional Copula function is used to analyze the occurrence time and flood peaks magnitude of the main and tributaries of Xiangjiaba-Three Gorges interval, and the inflow of the Three Gorges Reservoir is calculated. Further, the mathematical statistics method and the improved Fisher optimal segmentation method are adopted to divide the flood season, and then the flood limited water level of flood season is calculated by flood regulation. Finally, the risk of flood control and benefits are compared and analyzed.The results show that the flood season of the Three Gorges Reservoir can be divided into three periods: the pre-flood season from June 10 to June 30, the main flood season from July 1 to August 31, and the post-flood season from September 1 to September 30. The corresponding flood limit water levels are 159.1, 148.7 and 159.2 m, respectively. Without increasing the risk of flood control, the flood season can increase water storage by 180.20×108 m3 and the power generation by 10.33×108 kW·h.