A method of solid modeling for spiral bevel gear is purposed based on points cloud calculation，conjugate tooth surface and transitional surface of spiral bevel gear can be described exactly by this method. Solid model of gear with variable precision was established by changing density of points cloud. A method for shape evaluating of conjugate tooth surface was purposed by dimensional analyzing of contact ellipse, which was used to weaken randomness of the conventional evaluating method. Some measuring positions were chosen on the tooth surface, tooth surface was cut into a certain distance by sphere and contact ellipse was obtained by Boolean operation between solid model of gear and sphere. The principal curvatures and principal directions of measuring points were calculated by using formulas of induced normal curvature and induced geodesic torsion, radii of contact ellipse were measured along principal directions of measuring points. Solid model of gear which satisfies the requirement of tooth contact analysis is obtained by adjusting density of points cloud.