Abstract: Rainstorms and floods occur frequently in the Sichuan-Chongqing reach of the upper Changjiang River, exhibiting significant seasonal variations.Scientific and rational flood season division is crucial for the effective utilization of flood resources.In this study, we divides the flood season of the Sichuan-Chongqing reach based on daily rainfall data of this region and streamflow data from key hydrological stations such as Lizhuang and Cuntan Station.Further investigation was conducted on the relationship between the Meiyu in the middle and lower reaches of the Chanjiang River, the autumn rain in west China, and flood control and water storage in the Sichuan-Chongqing reach.The results indicate that the flood season can be divided into three phases: the early flood season from early May to mid-June, the main flood season from late June to late August, and the late flood season from early September to early October.The onset of the Meiyu is concentrated in June, while its retreat occurs mainly in July.After the end of Meiyu, the probability of concurrent flood events occurring in the upper and middle-lower Changjiang River reaches is extremely low, therefore the flood control storage capacity reserved by large upstream reservoirs can be gradually released.The autumn rain begins in late August and causes autumn floods in the Sichuan-Chongqing region, although the magnitude and frequency of these floods are significantly lower than those in summer.Since the autumn rain period coincides with the late flood season, it is crucial to ensure flood control safety while maximizing the utilization of autumn rain in west China flood resources to enhance reservoir storage levels.