The urban rail transit system in Chinese metropolis is developing into the network operation and structure optimization stage. With the high frequency of Critical equipment failure, equipment intelligent maintenance management needs highlighted. The paper puts forward a method of the evaluation of critical equipment health status in urban rail transit signal system with the needs of overhaul line in Shanghai urban rail transit. The method introduces the equipment service safety concept and defines the health status. Then the paper builds the multi-layer hierarchical structure model of equipment health status combining with considering the multi-dimensional influence factors of signal system equipment such as physical characteristics, economic characteristics and technical characteristics. Finally, the technical process of the fuzzy comprehensive evaluation of equipment health status is put forward. While take the switch which is the critical equipment of urban rail traffic signal system as an example to validate the proposed approach. The results show that the assessment consequence of the proposed method is consistent with the realistic expectations. The method can provide the reference for the diagnosis of hazard factors in service safety while quantitatively analyzing the equipment serving safety level.