Abstract: Applying the 2D hydrodynamic model to simulate the tide currents in the study area of Sansha Bay,this paper investigated the distribution of currents based on the topography in 2014,and discussed the situation in 1974 on different environment.The present study also analyzed the characters of tide currents between 1974 and 2014.As the results revealed,the currents in Sansha Bay was rectilinear flow,whose direction was dramatically affected by the topography and which reflected the character of terrain in Sansha Bay.The magnitude in deep groove or bay mouth was larger than that in shallow and was over 1.0 m/s,but less than 0.5 m/s in others.Generally,the magnitude in ebb tide was larger than that in flood tide.By contrast,the land reclaim over several years has affected the bathymetry and currents in Sansha bay,excepting the magnitude increasing in some area.Most of the areas decreased with ranging from 15% to 30%,but with less change for direction.