The new type of bilateral traction power supply system of traction substation groups can reduce the number of neutral sections, increase the distance of the power supply arm, and improve the power supply capacity. Furthermore, it provides a solution to the setting of neutral sections in the construction of electrified railways in the western and dangerous mountainous areas. At present, the system is still in the stage of theoretical verification and experimental exploration. In the simulation system, it is difficult to achieve the dynamic change process of traction network impedance caused by train movement. To address this issue, a simulation method of traction network impedance based on the voltage source converter (VSC) is proposed. By controlling the equivalent impedance of the alternating current port of VSC, the change in the impedance of the traction network at both ends of the train in the physical system is simulated, thus realizing the experimental simulation of the dynamic operation process of the trains. The proposed method is employed to build a system simulation model in MATLAB/SIMULINK. The simulation results indicate that the proposed method is able to simulate the dynamic changes in the traction network impedance when the train is under various working conditions. Moreover, the proposed traction network impedance simulation method is conducive to the further exploration and validation of the new type of bilateral traction power supply system of traction substation groups.