Abstract: The dynamic characteristics of wind turbines are greatly influenced by the flexibility of transmission system of wind turbine.In this paper,finite element method（FEM）is used to construct an analysis model considering the flexibility of transmission system of wind turbine gearbox,coupling and generator according to the basic theory of multi-flexible body dynamics. According to modal analysis theory,a method based on vector displacement cloud map is proposed to screen the torsional vibration frequency,and the torsional vibration modes from low frequency to high frequency of wind power transmission system are obtained. Campbell diagram and energy ratio are used to identify the resonance points of the system. The results show that the dynamic model of multi-flexible body plays an important role in accurately evaluating the dynamic characteristics of wind turbine transmission system.Under different excitation frequency loads such as 1.33,39.16 and 241.30 Hz,the transmission system of wind turbine has resonance modes at different positions such as gear spindle,generator rotor and secondary solar wheel shaft.The calculated results are highly consistent with the engineering practice,and the analysis method can provide theoretical basis for optimal design of wind turbine transmission system.