Based on the principle of gear meshing and differential geometry theory， the motion coordinate conversion relationship between the gear cutter and the non-circular gear tooth blank is obtained， and the machining process of the non-circular gear tooth profile is simulated. At the same time， in view of the impact vibration and noise problems in the process of non-circular gear transmission， a precise， efficient and general modification design method of non-circular gear tooth profile is obtained by taking the modification of gear shaping cutter as the means and the modification of non-circular gear tooth profile as the purpose. The kinematic simulation of the non-circular gears before and after modification is carried out using the dynamic simulation software. It is obtained that the impact vibration phenomenon of the modified non-circular gear in the transmission process is significantly weakened， which verifies the correctness of the modification method. It can reduce the tooth surface wear and increase the service life of the gear tooth， providing an important theoretical research method and design basis for the practical application and development of the non-circular gear.