Abstract: This article introduces a kind of new mechanicalstepless speed regulating system, which uses the ggroscopic effect of a rigid body with a fixed point and planetary wheel system's kinematics characters. Theauthor has made a study on the system's work principleand the system's parameter andperformance. The new system has a very good performancesuch as simple structure, constant power, high efficiency,self-adapting, and infinitely variable speeds, etc. The systemcan be used in the fields of automobile, shipping, and machine tool,etc; it will have a wide application prospect.