Typical local species Phragmites australis and invasive species Spartina alterniflora are selected in this study. We quantify how their morphological properties and the biomechanical properties of root, stem and leaves are affected by wave exposure during the growing seasons. Results show that the stem diameter of both P. australis and S. alterniflora growing with the wave is significantly higher than that of the control group (P=0.008,P=0.03). S. alterniflora shows a higher tensile or bending force than that of P. australis while the stress or static bending strength is lower. The higher equivalent stress contributes to the rigidity of P. australis although S. alterniflora owns a thicker individual. Furthermore, lignin and cellulose of P. australis are higher than that of S. alterniflora (P<0.001). Overall, plants have undergone significant changes in morphological characteristics, and the biomechanical characteristics of plants are closely related to structural compounds. The results assess the potential of plants in coping with the impact of waves, as well as provide a case in plant biomechanical study in coastal wetland protection and restoration research.