Conventional electromagnetic repulsion mechanisms (ERMs) are unsuitable for long-gap, high-voltage vacuum interrupters due to rapid force decay and over-reliance on inertial motion. While existing methods increase initial force, they exacerbate mechanical stress. This study proposes a stepped accelerating repulsion mechanism (SARM) to enhance performance and reliability. A simulation model was developed and optimized. Results demonstrate that, under the condition of the same repulsion peak, the conventional ERM cannot complete the 60 mm opening stroke due to the influence of the resistance. In contrast, the full travel time of the SARMs before and after optimization is 12.22 ms and 7.81 ms, respectively, which is shortened by 36.1% after optimization.