Abstract: Power connectors serve as core components for electrical power transmission between metro vehicle subsystems. During operation, the electrical contact performance tends to degrade or even fail under the combined effects of vibration and electrical current. However, the mechanisms and patterns governing the electrical contact degradation in power connectors remain unclear. Power connectors commonly used in metro vehicles are investigated. A high-current-vibration comprehensive test system is constructed to simulate actual operating conditions, and the evolution of electrical contact characteristics under different connector types and fixation methods is investigated. The degradation mechanism of electrical contact performance in power connectors is further explored by combining morphological characterization and phase analysis. Circular connectors showed greater stability and reliability than rectangular types. Under short-distance direct fixation, the electrical contact condition remains relatively stable during the initial vibration stage, but once wear on the contact surface accumulates to a certain extent, the degree of electrical contact degradation increases rapidly. The vibration-induced wear primarily progresses through four stages: Initial stability, followed by resistance fluctuations due to dynamic destruction and regeneration of the surface film, then a rapid rise in contact resistance caused by accumulated damage, and finally entry into a cyclic degradation process of “damage diffusion-short-term stability-re-deterioration” until complete coating wear leads to electrical contact failure. The degradation patterns and physical mechanisms of electrical contact performance in power connectors are revealed, providing significant engineering application value for enhancing the safety of urban rail transit systems.