Since the sediment runoff in the Yangtze River Basin has greatly decreased，this study analyzes the general changes in tidal flats in Yangtze River Estuary before and after the operation of the Three Gorges project based on the measured topographic data and finds that the high tidal flats increase，while the medium and low tidal flats decrease.The relationship between tidal flats in Yangtze River Estuary and wading engineering can be divided into four categories.Specifically，in terms of tidal flats that have been enclosed，the areas of high，medium，and low tidal flats are greatly reduced.In terms of tidal flats with built projects，the high tidal flats increase.The medium tidal flats decrease greatly，and the low tidal flats decrease slightly.In terms of tidal flats affected by surrounding projects，the evolution of the tidal flats is related to the relative position of the projects，the river regime of the tidal flats，and hydrologic and sediment conditions.In terms of tidal flats undergoing natural evolution，the high tidal flats increase，and the medium and low tidal flats decrease.The results show that the reduction of sediment inflow in the basin is the driving factor of the tidal flat evolution in Yangtze River Estuary，which has the characteristics of large range，long period，and slow change.However，human activities are the factors triggering the evolution of the tidal flats in Yangtze River Estuary，which have the characteristics of local range，short period，and drastic change.