The torque reduction and torque recovery of the clutch-less AMT used in electric vehicles will cause torsional vibration of the transmission system. Improper torque reduction adjustment will also adversely affect subsequent shift control. In order to improve the shift quality， the dynamic mechanism and control method of the two stages of torque reduction and torque recovery in the shifting process are studied. A torsional vibration model of the transmission system and a synchronizer meshing gear model are established， with the excitation law of torsional vibration during the shifting process being analyzed， and the influence mechanism of the inadequate torque reduction effect on vehicle dynamics and damage to the actuator during the gear shifting process being revealed， A torque controller according to the characteristics of the second-order system and a virtual system based on the initial state assumptions of the system are designed， with and the system torsional vibration suppression and initial state estimation of the torque control process being realized. Finally， the torque reduction and torque recovery control effects simulation are completed. The research shows that the designed controller can configure the damping ratio of the system by adjusting the control rate coefficient to obtain different torque control characteristics. When the damping ratio coefficient is close to 1， it can effectively reduce the torsional vibration during the torque reduction phase and the torque recovery phase.