Abstract: This paper investigates systematically the structural deformation characteristics of composite hydrofoils with own unique properties by numerical method to solve the fluid structure interaction problem on the composite hydrofoils. It establishes a numerical model of composite hydrofoils with fluid structure interaction in this study, which verifies the correctness of the numerical model by comparing the calculated results to the experimental results of Zarruk, and the numerical results show that the tip torsion angle of the composite hydrofoils increases with the increase of the Reynolds number. This paper investigates and analyses systematically the influence of the ply angle on the hydrodynamic performance and strength performance of composite hydrofoils in view of the numerical method. The results illustrate that the tip torsion angle of composite hydrofoils decreases with increasing the ply angle, while the tip displacement of composite hydrofoils decrease firstly and then increase with increase of ply angle. The study proposes two dimensionless, the dimensionless torsion angle and the dimensionless displacement, to eliminate the effect of engineering constants of composite on the structure deformation of composite hydrofoils, which is used to further investigate the influence of the bending-torsion coupling effect on the deformation characteristics of the composite hydrofoils. The strength of the composite hydrofoils is judged and studied by using the Tsai-Wu failure criterion. The numerical results show that the Tsai-Wu coefficient of composite hydrofoils decreases firstly and then increases with the increase of the ply angle, where the lowest Tsai-Wu coefficient and the largest Tsai-Wu coefficient appears in the 0^\circlayered composite hydrofoil and the 50^\circlayered composite hydrofoil, respectively.