A face milling method to rough processing the pinion of cycloid bevel gears is introduced. On the basis of the difference between face-milling and face-hobbing,the universal mathematical model is established firstly,the high order Taylor expansion of each NC axis in the process of face milling is finished and the corresponding coefficients are calculated. Aiming to reduce the deviation between the roughing surface and the finishing surface,an objective function is structured to optimize all of the coefficients and the related program is written out. A pair of gears is used to analyze the deviation from a theoretical point of view. Finally,the simulation processing is carried out,the feasibility and the correctness of the proposed method are verified.