Based on the orthogonal face-gear tooth surface equation, analyzes the relationship of maximum outer diameter coefficient, minimum inner diameter coefficient and the coefficient of maximum tooth width with the cutter teeth and gear ratio by Matlab software. According to the analysis of tooth surface equation, the tooth width and tooth height are discrete, calculates the coordinates of the points of tooth surface, and then draws the whole tooth pattern; Compared with face-gear real tooth surface, proves that the model established by the discrete method has higher accuracy.