Abstract: In the flood season of 2020, Poyang Lake suffered from a super-historical flood, and several hydrological stations in the lake area showed super-historical flood level, the maximum water level of Hukou station reached 22.49 m. The Zhongzhou polder, Wenguidao polder in Changjiang River and Sanjiaolian polder in Xiuhe River all breached. 185 semi-restoration polders were used to store flood water, and Jiangxi Province suffered serious flood disasters. In this paper, the daily average water level series of Hukou station in the flood season(from July to September) from 1998 to 2020 were selected for analysis. It was found that the average water level of Hukou station from July to September in the flood season of 2020 was the highest in the past 20 years. After preprocessing the collected Sentinel-1 remote sensing image from June 20 to August 31, 2020, the improved SDWI water index method was used to extract the water body area in the study area. The correlation between water area and the daily average water level of Hukou station and the temporal and spatial variation of water area were analyzed, and the inundation condition after the polder dike breach and use of semi-restoration polder was analyzed. Then, the reasons why the water level of Hukou Station did not exceed the guaranteed water level and avoidance of use of flood storage and detention areas near the Hukou Station were preliminarily analyzed. The research results can provide reference for future Yangtze River flood control.