Abstract: The metro gearbox mainly consists of the housing, bearings, and gears. During operation, the transmission components are subject to cyclic excitation and are particularly prone to failure, accounting for about 90% of all gearbox failures. The unreliability of conventional systems can significantly impact vehicle safety. This paper employs appropriate calculation models to investigate the reliability of gears, bearings, and the housing, and proposes a theoretically based reliability method. The effectiveness of this approach is verified, and the results provide valuable guidance for the design of gears and housings, as well as the selection of bearings for metro gearboxes.