Dynamic stress of wind turbine blade has great influence on its reliability and fatigue life. In order to decrease the magnitude of dynamic stress, frequency modulation method is often used to avoid resonance. This paper created composite material model for a wind turbine blade. Blade model was imported to abaqus environment for modal analysis. In view of the characteristics of fiber reinforces plastic, a mesh was built to carry out the model analysis, and the first 6 orders of the vibration frequencies and mode shapes were obtained, by imposing certain bound on the root of blade. Meanwhile, The analysis results of the composite material blade considering stiffening effect were obtained. This method can shorten modeling time and improve working efficiency, and also it is the base for blade structure calculation and check and new product developing.