In order to deal with the problem of uneven power distribution caused by the mismatch of line impedance of the parallel converter when the reactive power of the locomotive load changes suddenly in the off-grid traction power supply system, a power sharing strategy is proposed. Firstly, a parallel model of single-phase converters was established. The principle of droop control of grid-forming converters and the defects of traditional droop control were analyzed, revealing the reasons for introducing the improvement strategy. Then, the composition of the total output impedance of each traction converter and its influence on reactive power distribution were analyzed. A power sharing module was added to the traditional reactive power-voltage droop loop to achieve the average distribution of reactive power. Finally, the reactive power waveforms output by four converters with and without the improvement strategy were compared through MATLAB/Simulink simulation, verifying the effectiveness and accuracy of the proposed strategy.