The noise of extended-range electric vehicles is an industry concern, with the range extender providing the main noise source. Suppressing torsional vibration is important for reducing the noise of the range extender. A new combined model of system dynamics, generator control, range extender control, and active vibration control is proposed. The working state and torsional vibration characteristics of the model were analyzed under typical working conditions for the start, idling, stable operation, and stop stages. Under steady-state working conditions, for example, idling and stable operation stages, the torsional vibration of the range extender is mainly related to the excitation torque fluctuation of the engine, and when switching the operation stage (e.g., from idling to stable operation), it is mainly related to sudden changes in the generator and engine torque. An active vibration control model—including active torque composition controllers for engine torque fluctuation and switching the operation mode—is established. The simulation showed that active control effectively improved the torsional vibration and provided a new concept for controlling torsional vibration.