Tooth stiffness of face gear is one of the components of meshing stiffness of face gear drives. Its resolve can build excellent base for calculation method of meshing stiffness and analysis of dynamic for face gear drives. Based on Buckingham’s standpoint, along the length direction of the tooth of face gear, any one of its sections can be considered as a section of rack with varying pressure angle. According to above theory, the tooth form of face gear is simulated successfully. The method of calculation of the tooth’s stiffness of face gear is obtained. Compared with conclusion of tooth’s stiffness by FEM in the same parameters, it is proofed to be correct. Through analysis of influence of tooth’s stiffness by main design parameters of face gear, the benefit conclusions are drawn. That is, the changing ratio of tooth’s stiffness decreases with the increase of module, and the tooth’s stiffness increases with the increase of pressure angle but the changing ratio almost remains constant. The tooth’s stiffness increases with the increase of tooth width and the influence of changing ratio from tooth root to tooth crest is bigger than that of pressure angle.