The traction return system of high-speed railways comprises multiple conductors, including rails, protective wires (PW), through ground wires, and substation ground grids, making it difficult to accurately calculate the impedance parameters of each return path. To address the deficiencies in existing methods for calculating return current proportion of each path in high-speed railway traction return systems, a modified formula that is more consistent with practical engineering conditions is proposed. Firstly, the resistance and reactance matrices of the traction network and return system are derived based on multiconductor transmission line theory. Subsequently, a high-speed railway traction power supply system model is established on the Simulink platform to simulate the current proportion of each return path under normal operating conditions, and the effects of substation grounding grid impedance, return feeder impedance, and through ground wires impedance on the return current proportion of the substation ground grid are analyzed. The results show that the sum of the return currents through the rails, PW, and through ground wires accounts for approximately 69% of the total return current, while the return current through the substation ground grid accounts for approximately 31%. Among all factors affecting the percentage of substation ground grid return current in the total return current, the substation ground grid impedance has the most significant impact. Finally, engineering measures are proposed to reduce the proportion of return current flowing through the substation ground grid. When the traction substation ground grid and through ground wires cannot be altered, shortening the return cable lengths of the rails, PW, and through ground wires is the most effective measure for reducing the grounding grid return current proportion.