Ocean environmental corrosion and mechanical load vibration introduce considerable negative effects caused by the fluid-structure-environment interaction. A new design scheme for a blade with salinity corrosion resistance and mechanical fatigue resistance is proposed, based on numerical simulation and fatigue tests. The one-way fluid-structure interaction (FSI) model for an ocean current turbine blade was established and calculated by a computational fluid dynamics (CFD) solver and finite element method (FEM) solver. According to the FSI results, the maximum equivalent stress and deformation in extreme operating conditions are found to be within material and structural limits. On this basis, an aluminum alloy/nano particles reinforced polypropylene multilayer composite blade was designed and fatigue tested. The results show that an obvious crack-resistance effect exists within a certain stress range, and there is basically no change in the fatigue crack growth rates of NPRP in the four environmental fatigue tests. The multilayer composite blades with immersion pretreatment can stand 1 × 107 cycles of fatigue tensile loads and torque loads without failure. The results provide specific theoretical guidance for the optimization of the structural design of ocean current turbine blade in ocean environment.