According to the principle of gear meshing, analyzed the formation of the face-gear tooth surface. Calculated the tooth surface curvature and the induced normal curvature and expounded the influencing factors. Derived the trajectory equation of point contact orthogonal face-gear drive. Calculated the size, direction and contact force of face-gear meshing area, simulated the contact area and found the traces of face gear tooth contact biased towards the inside of the tooth, and verified it through the meshing test. This conclusion provides a basis for the reasonable design and application of face gear.