Femtosecond laser machining has become a new research direction for complex gear manufacturing. In this paper, the laser incidence angle θ at each node is measured and calculated by using the three-dimensional model of the tooth surface, and the ablation model of the tooth surface material 18Cr2Ni4WA with femtosecond laser machining is established to study the ellipsoidal ablation spot area, ablation area, and the depth of ablation pit and other tooth surface topographic features. Through the model simulation and experimental results analysis, it is shown that the ablation spot area increases slowly at first and then rapidly with the increase of θ. And the area of ablation zone increases with the increase of laser power P, and decreases slowly at first and then accelerates exponentially with the increase of θ. The ablation pit depth increases with the increase of P and decreases approximately linearly with the increase of θ. The influence of θ on the tooth surface quality is greater than that of P. When the smaller θ and P is around 4.9 W, the better tooth surface morphology is achieved, which provides technical support for improving the machining quality of face gear.