Abstract: As the safety guardian of modern railway systems, vacuum circuit breakers used in electrified railways have the advantages of being environmentally friendly and maintenance-free. However, during the long-term service, they are inevitably affected by extreme environment and operating conditions. To ensure the rapid removal of large current short-circuit faults, this paper takes 27.5 kV/2500 A/31.5 kA railway specific longitudinal magnetic vacuum circuit breaker as the research object. Based on relevant GB/TB standards, a combination of three-dimensional electromagnetic field numerical simulation analysis of vacuum interrupter and prototype experiment is adopted, considering the combined effects of structural uncertainty and operating condition uncertainty. The magnetic blowing characteristics before current zero are quantitatively analyzed, and the influence mechanism of voltage dispersion of the power supply for spring operated mechanism opening operation on the post zero breakdown performance is explored to provide a theoretical basis in the design of vacuum circuit breakers for electrified railways.