A physical model experiment was carried out in the laboratory flume to study the wave attenuation characteristics of tidal flat, vegetation and mangrove ecosystem, while the wave-height attenuation contribution of tidal flat to the mangrove ecosystem was quantitatively analyzed. The results show that with the increase of vegetation submergence, the wave height ratio of tidal flat and mangrove ecosystem increases gradually, namely the wave attenuation effect is getting weaker and weaker. The wave height ratio of vegetation first decreases and then increases, and the wave height ratio of vegetation is much higher than that of other vegetation parts when the water level is in the center of vegetation canopy. With the increase of relative wave height, the wave height ratio of tidal flat first stabilizes around 1.0 and then decreases, and the wave height ratio of mangrove ecosystem gradually decreases, while the wave height ratio of the vegetation first decreases and then increases. With the increase of relative width, the wave height ratio of tidal flat first decreases slightly and then increases, but most of them stabilize around 1.0, while the wave height ratio of vegetation and mangrove ecosystem first increases and then decreases slightly. The contribution of tidal flat to the wave height attenuation of mangrove ecosystem increases with the decreases of vegetation submergence, and the maximum contribution can reach 63%. Wave propagation in the mangrove ecosystem is characterized by the nonlinear attenuation and the attenuation rate of wave height per unit length is much larger in the first quarter width than that in the last three quarters width of the vegetation belt.