Abstract: During the shifting process of hybrid transmission, the motor plays an important role due to its fast response and accurate torque control. However, it also leads to an excessive reliance on the motor, while neglecting the collaborative control of the motor and clutch. Therefore, there is still room for further improvement in the shifting quality of the hybrid system. In addition, the changing motor torque can easily cause a certain shifting impact at the moment of the clutch state transition, especially for the transition from sliding state to engaged state. In the meanwhile, due to the presence of multiple power sources, the influence of acceleration on the shifting process cannot be ignored. For these problems, this paper proposes a power-on upshifting control strategy for a two-speed series-parallel hybrid transmission, and the root cause of the shifting impact when the clutch slip is eliminated is analyzed. On this basis, a motor torque control method is proposed that is easily to be implemented in engineering, that is, when the target slip is reduced to the threshold ?ω1, set the motor proportional-integral (PI) controller output to zero to ensure that the motor output torque can be changed to zero when the clutch slip is eliminated so that the shifting impact here can be suppressed. Then the factors that affect the value setting of Δω1 are analyzed based on the dynamics model and verified by simulation and hardware-in-loop (HIL) test based on the control variable method. In addition, the influence of acceleration on the shifting process is analyzed, and corresponding control strategies are proposed to improve the shifting quality. Finally, the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) test is conducted on the vehicle model to compare the shifting control effects under different working conditions, which can verify the proposed effectiveness of the control strategy.