Abstract: The functions of coastal artificial islands have expanded from traditional land reclamation to comprehensive ecological enhancement. However, the construction of artificial islands can alter the depositional dynamic environment in local sea areas and possibly cause significant influence on the stability of the sandy coasts behind the island. Based on the differences in depositional dynamic mechanisms, the artificial islands can be categorized into three types: the wave diffraction-dominated type, the longshore current-blocking type and the erosion and siltation coexistent type dominated by tidal current behind the island. By taking the construction of five artificial islands, including the Putao Island of Qinhuangdao, the Lianli Island of Yantai, the Shuangyu Island of Zhangzhou, the Pearl Artificial Island in the South China Sea and the Riyue Island of Wanning, as typical cases, the mechanisms of the construction of artificial islands to the erosion and siltation of sandy coasts behind the island are analyzed. The results indicate that influence of the artificial islands on the sandy coasts and hydrodynamic conditions in the sea areas behind the island is complicated. Commonly, one dominant mechanism co-exists with multiple ones, rather than a single mode. The development of island-linked sandbars is jointly controlled by island size, offshore distance and water depth. A large nearshore island more easily leads to the formation of island-linked bars. Additionally, the coupling of extreme events such as typhoon with artificial island effect can also cause influence on the morphology of beaches behind the island.