Based on the measured underwater topographic data and the results of the mathematical model,we analyze the characteristics and causes of Jiangya south shoal regime evolution in South Passage of the Yangtze Estuary.The results show that the channel developed in the head of Jiangya south shoal,the lower segment of Jiangya south shoal silt towards downstream,and 5 m deep tail of the shoal extended downward and forms the maintenance difficult section of South Passage 5.5 m channel.Meanwhile,Jiangya north channel scours and develops mainly because of the water level difference between the main channel of South Passage and Jiangya north channel and continuous development of the South Passage riverbed.With the development and transfixing of the channel in the head of Jiangya south shoal and Jiangya north channel,new diffluent outlet will form in South Passage,which has an adverse effect on the regime evolution and channel regulation of South Passage.