Port construction will cause a certain impact on the marine environment，which will change the hydrodynamic conditions of the surrounding waters，and also have an impact on the water environment.The plane two-dimensional numerical model MIKE21FM is used to predict the impact of port construction on the hydrodynamic environment.By adding a two-dimensional unsteady convection diffusion module，the prediction of suspended solids diffusion is carried out.The material transport equation is used to predict the wastewater discharge，and the concentration field of typical pollutants is simulated by the difference numerical simulation method to analyze the impact of wastewater discharge on water quality. Under the cover of cofferdams，the fluctuating tidal current velocity in the port area is greatly reduced，and the velocity in each port basin is less than 0.25 m/s. The influence of reclamation dredging is mainly concentrated in the range of 300 m around the dredging operation point，and the maximum diffusion range of various pollutants discharged by waste water is controlled within 400m.The conclusion can provide reference and basis for the planning，design and construction of port area.