We establish a compatible three-dimensional tidal flow model in radial sand ridge area based on the unstructured grid finite volume coastal ocean model（FVCOM）. In order to make it better fit the complex irregular coastline boundary，we adopt triangle mesh in the horizontal direction，and apply the σ-coordinate in the vertical to simulate. The results show the simulated values are consistent with the observed values，and the model is better to simulate the spatial and temporal distribution of the tidal flow in radial sand ridge. The whole current field is dominated by north and south tides，and they converge and diverge towards Jianggang. The velocity of deep groove is large and concentrated，and the flow direction is consistent with the trend of deep groove. The direction of surface and bottom residual current in the north of Jianggang is coastal current from south to north. The coastal residual current in the south sea area is counterclockwise rotating current，and the residual current near the deep groove mostly directs to the deep groove.