As information， intelligence and miniaturization progresses in ammunitions， Micro-Electrical-Mechanical System （MEMS） based initiator was derived to meet the need of the information of energy-transferring， miniaturization on structure and integration of energy sequence. As one kind of a system-level MEMS initiator， the present micro fire-train was integrated based on initiation detonation mechanism of the flyer impacting the next booster explosive. By focusing on the application and technical requirements of micro fire-train， the state-of-art of the fire-train was reviewed from five aspects， including the micro-heater design and firing energy control， microscale detonation energy control and devitrization， energy transmission and safety control， micro fire-train design and integration， and reliability evaluation of the fire-train. Based on the analysis of state-of-art of micro fire-train， some suggestions for future development were proposed， and the key points for the further development of micro fire-train are discussed： strengthen the basic research of initiation and detonation mechanism under micro scale； promote digital engineering and improve forward-design capability； build mass production capacity including element-level， component-level and system-level of the micro fire-train； enhance the qualification and improve technology maturity of micro fire-train. It is vital useful for the peers to pay more attention on the design， fabrication， test and evaluation of the micro fire-train.