The cycloid gear is the key part in RV reducer,whose design and manufacturing level has a huge impact on the drive performance of RV reducer. At present,the manufacturing capacity of cycloid gear cant meet the need of mass production of RV reducers. In order to improve the processing efficiency,gear shaping was introduced to the machining of cycloid gear. According to the movement of gear shaping,the coordinate systems for cutting edge design were established.Based on the equation of cycloid tooth shape after modification,the equation of theoretical blade shape of gear shaping cutter was derived. Taking the cycloid gear in one kind of RV reducer as an example,the cutting edge design was carried on. The results show that the designed blade shape can contact with the cycloid tooth shape in every moment,proving that the proposed design method is feasible and effective.