Abstract: In this study, a coupled model based on unstructured-grid, primitive-equation, Finite Volume Community Ocean Model (FVCOM), the Mellor-Donelan-Oey (MDO) wave model and a stratified vegetation wave dissipation parameterization scheme is developed to study the mangrove wave attenuation capability. By comparing the scenarios with and without mangroves, the wave attenuation rate (A_r) is computed to study the wave attenuation capabilities of different mangrove morphologies under high and low water levels, and also to analyze the effect of plant density on their wave attenuation capabilities. It shows that A_r is nonlinearly and positively correlated with the width of the forests. The relationship between A_r and water depth is related to the structure of mangroves. For A-type mangrove (e.g., Avicennia marina), the maximum A_r at low and high water level is 67.9% and 94.4%, respectively. The maximum A_r of the B-type mangrove (e.g., Rhizophora stylosa) are 90.6% and 89.4% at low and high water-levels, respectively, while the WAR of the C-type mangrove (e.g., Ceriops tagal) is not significantly different at high and low water levels. The study also found that an increase in plant density can increase the upper limit of A_r. It makes the A_r more sensitive to the changes of forest width and the forest width is thus reduced to reach the maximum A_r. The study shows that the performances of wave attenuation by different mangrove morphologies should be considered in the conservation of mangrove ecosystems.