Based on the theory of mechanical dynamics,the influence on dynamic characteristic of transmission is researched when the tooth generated elastic deformation under load.First,in order to build the transmission dynamic analysis model,the stiffness matrix,mass matrix and node positions information of the transmission box are extracted and combined with transmission part virtual assembly.Then,the mesh misalignment,transmission error and tooth contact condition caused by elastic deformation of tooth are calculated.The effect of tooth elastic deformation on meshing quality of gear pair and dynamic characteristic of transmission are analyzed.Finally,according to the theory of elastic-mechanics,the meshing quality is improved through modification of tooth profiles to achieve the purpose of decreasing the dynamic response of gear pair under load.These results provide references for reducing the elastic deformation of tooth effectively and improving the dynamic characteristic of transmission.