[Objectives] The degree of bending-torsion coupling deformation of composite propeller reflects the stiffness characteristics of blade , and there is a certain correlation between the blade stiffness and its hydrodynamic characteristics . In order to optimize the fiber layer of composite propeller from the perspective of stiffness , [Methods] 4383 composite propeller was taken as the research object . Based on the fluid-solid coupling self-iterative algorithm of composite propeller , the numerical calculation method of blade stiffness was constructed , and the bending stiffness and torsional stiffness of unidirectional fiber cloth and orthogonal fiber cloth laid on the blade at different angles were numerically calculated . [Results] The numerical calculation results showed that the thrust coefficient difference and blade stiffness value of composite propeller showed a relatively synchronous change rule ; The minimum thrust coefficient difference of composite propeller with orthogonal fiber cloth is larger than that with unidirectional fiber cloth . When the elastic modulus of the material decreases , the stiffness value of the blade decreases , and the difference of the thrust coefficient of the composite propeller decreases . When the blade stiffness is small , the blade can better play to the advantages of adaptive flow field , through the bending and torsion coupling can produce greater pitch deformation , thus in the high and low wake region produce smaller periodic thrust pulsation than the metal propeller . [Conclusions] The results can guide the optimization design of composite propeller to improve the hydrodynamic performance after ship .