Abstract: In order to solve actual usability problems of programs used in the modification process of face gear based on preset contact trace, this paper has explored whether modification in tooth width direction has different effects compared with modification in the normal direction which has the advantages of programming feasibility and high operation efficiency. The equation of tooth of face gear was established in this paper; MATLAB was used to finish the program of the modification in tooth width direction and normal direction respectively. The visual surface picture of modification was accomplished and CATIA was used to build the 3D models. At last, ABAQUS was used to simulate the tooth contact analysis of the two ways and the simulation results was analyzed. The result shows that modification in tooth width direction can get a wider contact area; but the contact region of modification in normal direction distributes closer to the root of face gear, more in line with the mechanical characteristics of the face gear. Therefore, if the strength of face gear is enough, modification in tooth width direction can be used to replace modification in normal direction, which will be beneficial to the further programming of the transmission error study.