Abstract: As an important coastal wetland plant, mangrove and its biogeomorphologic process are crucial for coast protection. In order to study the sediment transport mechanism near the bottom of a mangrove, hydrodynamic observations were carried out in the Zhangjiang Estuary, Fujian Province; and the hydrodynamics and sediment transport between the bare flat and mangrove were studied.The results indicate that tidal current speed was obviously decreased and deflected by mangrove, and prominent sediment deposition and resuspension observed at the bare flat, and sediment deposition predominates the mangrove. It means that the mangrove has the capability to trap sediment from movement.Further more, the calculation of the transport equation also shows that the sediments on the bare flat were transported towards the mangrove through tidal creeks, and then intercepted by mangrove, implying that the mangrove exerts significant effect on siltation through reducing water movement and plant adsorption.