Considering the integration of the drive motor and transmission system of the electric drive axle of a commercial vehicle, the system integration is high and the vibration coupling between components is outstanding, at the same time, due to the complexity of the rigid-flexible coupling vibration analysis model of the electric drive axle, resulting in a long computation time and a greater difficulty in simulation and analysis. In this paper, for a heavy commercial vehicle electric drive axle, a lightweight rigid-flexible coupling dynamics model is constructed, and its vibration characteristics are analyzed. First, the electromagnetic excitation force of the drive motor at different speeds is calculated using the finite element method. After that, the rigid-flexible coupling model of the electric drive axle is established using the lumped-parameter method and the finite element method. And the model order reduction method based on modal superposition method was used to reduce its order. The torsional vibration characteristics of the electric drive axle were analyzed using a relatively lightweight model. Finally, Color maps is generated using the surface vibration signals of the housing and the torsional vibration characteristics of the electric drive axle are analyzed. The simulation calculation results show that the reduced-order model can relatively accurately reflect the torsional vibration characteristics of the electric drive axle, while also reducing the calculation time.