Abstract: The importance of urban rail vehicle fault is analyzed with FMECA (failure mode, effects and criticality analysis) method, through quantitative calculation of the importance of each vehicle fault mode, the impact of critical faults is recognized, which provides support to develop scientific and effective maintenance outline for vehicle systems. The method is applied to analyze the light rail vehicle bogie and braking system faults in Changchun City, and the results show that the top three important faults of the bogie system are the stent crack in bracket, the caliper looseness or ball valve stuck in the height valve, the disengagement or standard-exceeding cracks in anti\|roll torsion arm. While the top three important faults of the braking system are sanding system failure, brake unit failure and brake clamp failure. Therefore, the top three important fault modes should be concerned with emphasized attention in the development of daily maintenance outline.