A wind turbine multibody dynamics model, which based on lumped mass method and Lagrange equations, has been built to research the elastic mounting of the gearbox effect on the dynamics characteristics of the drive train after considering the flexible connection characteristics of the gearbox elastic mounting in the horizontal axis wind turbine. With the help of the dynamic model and the modal analysis method, the modal natural frequency has been obtained after coupling the system with gearbox elastic supporting, and the modal energy distribution by this method has been gotten. Using variable parameter of the gearbox elastic mounting, sensitivity of the drive train modal characteristics analysis is performed, and the dynamic response of gearbox housing is calculated with mode superposition method. Numerical solution and analysis show that the modal natural frequency of the drive train system is the main gearbox mounting vibration modal caused by the gearbox elastic mounting, Linear stiffness of the mounting has an impact on the low natural frequency of the drive train, It is reasonable to consider the first and second order modal of the system when doing the vibration analysis of the gearbox mounting. This research provides a theoretical basis on the reliability design of the drive train and damped control which suppress the vibration of the drive train.