Abstract: The structural flexibility of gear,shaft and housing will affect the meshing stiffness and supporting stiffness,which are the most important internal excitation of the dynamic response of gear systems. To investigate the influence of flexibility of different components on the dynamic response of the system,taking a 8 MW large-scale wind turbine gearbox for instance,the full flexible multibody dynamic model of gear transmission system is established. Three flexible multi-body dynamic models are developed by modeling specified types of components as rigid bodies. The effect of the structural flexibility on the dynamic response of the system is studied by using time-domain and frequency-domain analysis method. The results show that the housing flexibility is the most significant factor affecting the dynamic response of the system;the flexibility of shafting does not affect the meshing frequency of gears in adjacent stages,and the gear flexibility also does not affect the appearance of the side frequency band with the shafting rotary frequency feature. The extraction of these two frequencies is an important prerequisite to identify the system characteristics and working states.