A path analysis method of the laser ignition system was investigated. First，an optical transmission model was given for the single optical path，and an analysis method was proposed by analyzing the effect of the number of optical connectors on the insertion and reflection loss. The criteria of the optical path for different number of connectors and work of laser explosives was deduced to improve the adaption and precision of the method. The experiments of ignition proves the correctness of the proposed method，which provides a reference for the design of onboard controlling computer software of launch vehicle.