Based on the hobbing process simulation of non-circular gears, a method for obtaining the precise tooth profile and evaluating the undercutting characteristics according to the profile generated after the finite number of envelop is proposed. The profile points formed by different hobbing strategies are compared, then the envelope method with uniform accuracy for all teeth is selected. The formation rule of tooth profile morphology is analyzed, and the pickup method with high convergence rate is proposed. The influences of the envelope number and gear parameters on the tooth profile accuracy are analyzed inductively, and the reasonable number of envelopes for expected accuracy is given. The results show that the tooth profile analysis method based on the hobbing process simulation can accurately acquire all feature points of the tooth profile and analysis the undercutting phenomenon.