Abstract: The coastal wetland is covered by abundant salt marsh vegetation such as Suaeda salsa and Phmites australis, but there is still a shortage of quantitative evidence of the effect of salt marsh vegetation on hydrodynamics, sediment transport and accretion in the coastal wetland area now. Based on the Delft3D hydrodynamic and sediment model and taking the estuary wetlands as the case study object, this paper quantitatively investigated how Suaeda salsa and Phmites australis plants communities influenced on the hydrodynamic characteristics of the watershed, sediment transport and deposition in the wetlands of the Liao River Estuary by means of numerical simulation methods. The results show that the salt marsh vegetation has a weak effect on the tidal levels during the flood and ebb tides, and a more obvious effect on the tidal current, and there are distinct differences in the influence of various vegetation types on the tidal velocity, and the Phmites australis plant has a greater attenuation effect on the tidal velocity than that of Suaeda salsa vegetation. The interception capacity of suspended sediments by salt marsh vegetation in different tidal periods shows great differences. The interception rate of suspended sediments by salt marsh vegetation is greater than that in the bare beach area.The interception amount of suspended sediments was expressed as: the neap period ＜ middle tide period ＜spring tide period. The deposition of suspended sediments causes the intertidal beach topography to show an accretion trend. It can be seen that the salt marsh vegetation in the Liao River Estuary can effectively accelerate the deposition of the beach and stabilize the beach landform.