During the flood season of 2022, the Yangtze River Basin have experienced high temperature, extreme drought, and very limited rainfall. The middle and lower reaches of the Yangtze River have experienced the lowest water levels in history along the main river, major tributaries and lakes. For example, both the Poyang Lake and the Dongting Lake have suffered from historically extreme drought and low water levels. Due to the general decrease in normal inflow of water in the middle and upper reaches of the Yangtze River Basin during the flood season, the Yangtze River estuary have experienced a rare summer saltwater tide intrusion. This paper takes the extreme low water level and corresponding flow rate of Datong Hydrological Station as the upper boundary conditions, establish a three-dimensional mathematical model of the Yangtze River Estuary to simulate the adverse effects of saline intrusion on the hydrodynamic process of the Yangtze River estuary under extreme drought conditions in the middle and lower reaches of the Yangtze River, including the range and degree of saline intrusion upstream of the estuary, and the characteristics of stable stratification in the intersection area of salt and freshwater in the Yangtze River estuary under dry water conditions, etc. The simulation results were validated using actual saltwater hydrological monitoring data during this period. This study provides relevant references for further research on the impacts of salt tide intrusion in estuarine areas on fresh water intake in Shanghai's water source areas, as well as the response of estuarine water quality and aquatic ecological environment.