Abstract: Based on the mathematical model of the coaxial parallel hybrid power system and the automatic diaphragm spring clutch, a torque tracking control strategy was presented for automatic diaphragm spring clutch, which include Kalman filter and cascade variable parameter PID controller. A variable parameter torque loop proportional controller was designed, the travel loop PID control parameters were optimized, and some simulation and experimental study on the torque tracking control during the HEV mode switching process were carried out. Results show that the proposed clutch torque tracking control strategy possesses better performance.