Tidal current not only has an important impact on the nearshore topography and seawater substances transport, but also plays an important role in fishery ecosystems. Sanya Bay is a large semi-enclosed open bay in the southernmost part of Hainan Island. In this paper, we used a high resolution, three-dimensional and non-static MITgcm model to simulate the barotropic tidal current in this area. During the simulation period, we found the tide level in the nearshore of Sanya Bay generally ranges from 126 to 130cm in high water and from -22cm to -18cm in low water during the spring tide. The results of tidal current ellipses showed that the surface tidal currents of the two diurnal constituents K₁ and O₁ dominant in clockwise rotation in most areas of Sanya Bay. The nearshore current is dominated by reversing tidal current, and its tidal current elliptic rotation rate is small. The maximum current velocity of K₁-tide is relatively large, about 0.4~0.5 m·s^-1, between West island and Sanya Bay. The current velocity of the two semi-diurnal tide constituents M₂ and S₂ are smaller than that of the two diurnal tide constituents. In the coastal area of Sanya Bay, the magnitude of tide-induced residual current is small and the velocity of Lagrange residual current is less than 0.02m/s. The eastward circulation current on the northeast side of West island changes direction as it encounters the near shore of Sanya Bay and Luhuitou Peninsula. This flow pattern is favorable for sediment and other water-borne substances to accumulate here. In nearshore of Sanya Bay, Stokes drift accounts for more than 30% of the Lagrange residual current and has a great influence on the transport of substances and energy in the nearshore area. Offshore, Stokes drift accounts for less than 10% of the Lagrange residual current.
 

Tide-induced residual current, spatial distribution, Sanya Bay