In this paper, a horizontal-axis ocean current turbine is taken as investigation object, to study the Fluid-Structure Interaction (FSI) effect at working conditions. With the help of finite element analysis software ANSYS, the pressure on the turbine is calculated in the flow field, which provide input loadings for static structural analysis before prestress modality analysis. The results show that the phenomenon of obvious stress concentration will occur at the root of the blade during wind turbine operation. The maximum stress will increase with the increase of flow velocity, which inevitably influence the modal characteristics of the turbine. The ocean current turbine generated power and thrust force are also investigated, and the results show that the optimal power is obtained when the Tip-Speed Ratio (TSR) is 5.