Abstract: Based on the runoff and sediment discharge data of Datong Station from 1960 to 2020, the seasonal and interannual variations and trends of seawater and sediment flux into the Yangtze River estuary were studied, and the influencing factors and their effects were discussed. Results show that during the data coverage period: the annual average runoff was 890.6 billion m³, and the annual average runoff fluctuated around the annual average with no obvious variation trend; seasonal variation of runoff into the sea was obvious, and the annual runoff from May to October accounted for 70.3% of the whole year; the annual average sediment transport was 335 million tons, and the sediment transport process showed generally a decreasing trend; the change of sediment flux into the Yangtze River estuary was obviously affected by the factors of water and soil conservation and reservoir construction. After the impoundment of the Three Gorges Reservoir, the sediment flux at Datong Station decreased by 62.8% compared with that before; the river regime of the Yangtze River estuary had also changed obviously due to the decrease of sediment flux in the Yangtze River basin. The sediment concentration in the estuary decreased significantly, the estuary changed from siltation environment to scour environment, the subaqueous delta front of the Yangtze River estuary occurred the large area of scour, and the estuary sandbar and the subaqueous delta sediment supply occurred the structural change of "sourcing-sink transformation".