The rolling Bearing planetary reducer with driving balls in one of the latest type in mechanical transformation. The speed reducing ratio results are obtained through experiments. Fluctuating factors of the speed reducing ratio results relative to the theoretical results are analyzed. The mechanical efficiency which is associated with the rotating speed is obtained by means of experiments. Meanwhile

many factors that affect the mechanical efficiency of the reducer are analyzed. Mathematical formula of the meshing efficiency is formed. The mechanical efficiency formula of the reducer is accordingly established. The improving design methods for this kind of reducer are proposed so as to increase its mechanical efficiency.