Abstract: The hydrodynamic and sediment environments near island coasts and its changes caused by coastal structures both have their own characteristics and complexity.According to the historic data,the changes of the process of hydrodynamics and sediment in the Shengsi fishery port area,caused by the builting coastal structures,are analyzed systematically.On the basis above a 2D mathematical model for sediment transport by waves and tidal currents is developed,and the changes of the tidal current field,sediment concentration field and the deposition-erosion caused by the proposed coastal structures are predicted and analyzed by the model.After the implement of the built and the proposed breakwaters in the fishery port area,the hydro-dynamic conditions are worse obviously and the seabed is deposited with a rate of 0.1-0.3 m per year.After the implement of the built and the proposed reclamation in the fishery port area,the hydrodynamic conditions are better and the seabed is eroded slightly.The effects on the hydrodynamic and sediment environments caused by both the built and the proposed coastal structures have a good consistency.