Through the establishment of two-dimensional unsteady hydrodynamic model of Zhanjiang port, this paper simulated the current for sea region of Zhanjiang port.Based on the verification of current,it established a suspended model of water quality prediction and forecasted the influences of suspended matter concentration on water environment in process of underwater work. It analyzed the impact of construction of the project on the sea water environment through calculating the area of exceeding the standard of suspended matter. The results show that the impact range of cofferdam construction is around 200 metersof sea field, the increment of concentration is from 10 to 400 mg/L, the highest concentration in center is 400mg/L and the extent of impact decreases from center to outside.