As an ecological buffer zone, the salt marsh plants growing in the coastal zone play an important role in reducing the current velocity, weakening wave energy and preventing coastal erosion, it is of great significance to investigate the mechanism of wave attenuation by salt marsh plants in estuaries and coastal zones. Based on the open source CFD software package of OpenFOAM software, a 3D numerical model considering the effect of vegetation on flow and wave was established in this study. Firstly, the model was applied to investigate the propagation processes of dambreak wave over the triangle obstacle and the solitary wave climbing on the sloping beach, the results show that the OpenFOAM model can accurately capture the propagation of dambreak waves and free water movement of solitary waves. Then this model was also used to simulate the formation, development and attenuation of solitary waves in a vegetated wave flume, where the wave height of solitary waves decreases obviously through the vegetation zone, the vegetation can effectively attenuate wave energy on a coastal beach. Lastly, the propagation process of sine waves on the vegetated beach was numerically studied, the obtained numerical results show that the attenuation of wave height is directly proportional to the incident wave height, plant density, the drag force coefficient of plant and the steepness of the coast.