Abstract: The alert switch failure and abnormal traction braking switch signal of the master controller on Beijing Subway Ba Tong Line are studied. Based on the existing design, the working conditions of the master controller alert switch and traction braking switch are modeled, simulated, analyzed and comparatively verified. It is found that a Schottky diode connected in parallel with the relay coil on the switch-controlled side can effectively reduce relay coil voltage fluctuation during switching and shorten relay action time, improving working conditions for alert switch and traction braking switch. Additionally, by increasing the transition angle of the master controller′s traction/braking switch signal and eliminating the signal overlapping area, the superposed failure of the master controller traction braking signal can be effectively solved on top of the existing design. The new design scheme improves the working reliability of the master controller alert switch and traction braking switch, effectively solving the problem of frequent failures in the existing design while elevating the Beijing Subway Ba Tong Line operation reliability.