In the realm of rail transit, the axle counter serves as a vital redundant signal device for precisely positioning vehicle position, thereby playing a pivotal role in ensuring the safe operation of the vehicles. This paper primarily delves into the anti-interference capabilities of the magnetic field associated with the axle counter in rail transit. It quantifies the resilience of the axle counter's magnetic field against external disturbances and translates this into specific requirements for the magnetic field emissions of the vehicles. This approach ensures compliance with electromagnetic compatibility standards within the integrated system of the vehicle and axle counter. Furthermore, this paper introduces the development of a dedicated detection device that assesses the anti-interference abilities of the axle counter. This device accurately measures the threshold of magnetic field sensitivity for the axle counter in various directions. Specifically, when the interfering magnetic field exceeds the inherent sensitivity threshold of the axle counter, it ceases to function properly. This innovative detection tool has successfully measured the sensitivity thresholds of axle counters from multiple manufacturers. By utilizing the device developed in this paper, we can systematically test the magnetic field sensitivity thresholds of different types of axle counters. This, in turn, allows us to formulate targeted index requirements for the magnetic field emissions of the vehicles. Such an approach significantly contributes to the systematic safety design of electromagnetic compatibility between trains and axle counters, thus enhancing the overall reliability and safety of the rail transit system.