Abstract: In general, a pair of clockwise and anti-clockwise vortexes will develop at the right and left sides of a headland (facing to the sea), respectively. These vortexes play important roles in sediment transport, sea bed change and pollutants' dispersion. The islands in the ocean will also induce island wakes. When the islands are close to the headland, the island wakes may interact with the vortexes induced by the headlands. In this study, we take the Puqian Bay, Hainan Island, as an example to investigate the construction of an artificial island at the bay mouth on the vortexes in the coastal bay, and further examine its effect on the sea bed erosion and accretion. This study is mainly conducted through using the COAWST model. The model is carefully calibrated by the observation data of water elevation and current. The model results indicate that there develops a large-scale clockwise vortex in the bay during the spring tide, while this vortex disappears during the neap tide. The construction of the artificial island does not change the vortex pattern as a whole, however, locally there develop several clockwise and anti-clockwise vortexes around the island. The sea bed is in a state of weak accretion under the tidal action, while the artificial island strengthens this pattern in most of the bay, except in the waterway between the island and coastline. It is hoped that this study will benefit coastal development management.