To analyze the impact of the construction of the Hengsha Dongtan (Phase 6-8) project on the Yangtze River Estuary, a two-dimensional tidal flow model was established using Delft3D, and tidal level and velocity calibration verification was conducted using existing hydrological data from 2008 and 2016. Based on the hydrological conditions in normal and flood years, the hydrological conditions, such as tidal volume, tidal level, and flow field in the main tributaries of the Yangtze River Estuary before and after the implementation of the Hengsha Dongtan Phase 6-8 Project were simulated. The results show that under two flow conditions, the construction of the Hengsha Dongtan Phase 6-8 project has a relatively small impact on the rising and falling tide flows of the main tributaries of the Yangtze River Estuary. The variation of high and low tide levels in the Yangtze River Estuary does not exceed 0.01 m, and the variation of high and low tide levels in the water area where the project is located does not exceed 0.02 m; The project has no significant adverse impact on the large-scale flow field structure of the Yangtze River Estuary. The rising tide velocity of the Beigang Waterway and Beigang Beisha Jiahong has decreased, with a maximum decrease of 0.03 m/s in Beigang Waterway and 0.02 m/s in Beigang Beisha Jiahong. The rising tide velocity of the Hengsha Channel and the North Channel of the Yangtze River Estuary has remained basically unchanged. Under the current riverbed terrain and engineering boundary conditions (all of the Hengsha East Beach project has been completed), there is a northwest southeast channel on the northeast side of the beach surface. The northern edge of the eighth phase project and the northern edge of the downstream sand body have a high ebb tide velocity, with a maximum velocity of 1.5 m/s or above, which is not conducive to the stability of the Hengsha East Beach regulation project.