Abstract: In 2022,the upper reaches of the Yangtze River suffered extreme drought, and the saltwater intrusion in the Yangtze River Estuary(YRE) was intensified, leading to a severe test on regional water security.To investigate the causes and countermeasures of saltwater intrusion under extreme drought, this paper analyzed salinity, tide level, wind speed and direction data during low water periods between 2019 and 2023,as well as runoff data from upstream Datong Station during the same period.Spearman correlation analysis and Chi-square analysis were employed to examine the process of saltwater intrusion in September 2022 and identify key influencing factors.The analysis results revealed that:(1) Due to extreme drought, the dry conditions of the main stream of the Yangtze River advanced to August 2022.Combined with typhoons and astronomical spring tides, the salinity of Chongmingzhoutou Station, Yanglin Station and Liuyao station in the YRE greatly exceeded the limit from September 2022 to April 2023,reaching 1.922‰,0.585‰ and 2.134‰.(2) The three salinity monitoring stations located in the YRE experienced varying degrees of saltwater intrusion based on their respective upstream incoming water conditions.When the discharge at Datong Station fell below 15 000 m3/s, different regions along the estuary would be affected by saltwater intrusion accordingly.(3) In October 2022,recharging fresh water for repelling saltwater intrusion were implemented during neap tide periods within the YRE.These measures resulted in an increase of discharge at Datong Station to over 12 000 m3/s after water replenishment and effectively compressed saline levels in the upper part of the southern branch.These findings provide theoretical support for analyzing factors contributing to saltwater intrusion across various areas within the YRE,and developing strategies for managing recharging fresh water for repelling saltwater intrusion.