Based on the finite element analysis method

considering the time-varying stiffness incentives and error incentives of the meshing gear pairs

the dynamic incentive curve of the internal gear pair is established.With the influence of the crack fault to the mesh stiffness of the gears

the internal dynamics incentive curve of the crack gear is established at the same time.The influence of the different location and extent of crack fault to the dynamic incentive is discussed.The results indicate that the influence of the deep crack to the internal dynamics excitation is higher than the shallow crack.And the influence to the internal dynamics excitation of the crack fault appearing on the tooth root is stronger than that on the sub-degree circular.