A wave-flow coupled numerical model under the influence of salt marsh vegetation was established using Delft3D software to quantitatively analyze the water and sediment dynamics and sediment deposition processes in the Liaohe Estuary tidal flat wetland. The research results show that the simulated wave, tidal current, and suspended sediment results are consistent with the measured data. The suspended sediment concentration at each measurement point gradually increases from the surface layer to the bottom layer. Different salt marsh vegetation types, such as Phragmites australis and Suaeda salsa , have significant differences in their effects on the tidal flat flow velocity. During the spring tide period, Phragmites australis can more effectively attenuate flow velocity. Compared to Suaeda salsa , Phragmites australis has a more significant effect on the interception of suspended sediment and sediment deposition.