Abstract: The reclamation project in the north of the Jintang Island has greatly changed the topography of its surrounding sea areas, and thus impacts the hydrodynamics in the sea areas. Based on observational data and numerical simulations, this paper analyzes the impacts of the reclamation project on tidal currents, residual currents, erosion, and deposition in the sea areas near the Jintang Island. The results show that the topography change has a great impact on the Ligang channel - its northern entrance shifts to the north and the current velocity at the entrance increases significantly. The maximum flood velocity increases from 0.50 m/s to 0.92 m/s, an increase of 84%, the maximum ebb velocity increases from 0.30 m/s to 0.53 m/s, an increase of 77%, and the residual current velocity increases from 0.05 m/s to 0.12 m/s, an increase of 140%. The maximum flood velocity at the central part of the Ligang channel decreases. The current velocity near the newly formed headland by the reclamation also changes significantly, with rotating flow field formed between the two headlands. The maximum flood velocity decreases from 0.46 m/s to 0.14 m/s, weakened by 70%, the maximum ebb velocity decreases from 0.61m/s to 0.17 m/s, weakened by 72%, and the residual current velocity decreases from 0.55 m/s to 0.04 m/s, weakened by 93%. The spatial distribution of sediment deposition in the sea areas to the north of the Jintang Island is consistent with that of residual current change, suggesting that they are closely related and significantly affected by the topography change.