A type of three-pitch fluctuating gear ratio limited-slip differential was presented for the first time, the working principles of it were analyzed, the tooth profile design method of using non-involute tooth profile and separated tooth profile design along the pitch line was introduced, performance comparison between vehicles equipped with three-pitch fluctuating gear ratio limited-slip differential and common open differential has been finished. The data from experiments proved that three-pitch fluctuating gear ratio limited-slip differential could increase the traction of a vehicle, improve its acceleration performance, decrease braking distance and limit sideslip.