Abstract: Constructed a spot collection system to collect the UV-VIS spectrum of liquid rocket plume, obeying relations between the engines status and faults, and diagnosing the liquid-propellant engines faults. Several tests testifying the feasibility of the system and the engine spectral data had been carried out. Through analysis, emission spectrum of metals, such as Fe were detected. The interrelationship between the engines status and the spectral intensity of plume were found, which testifying the feasibility of the proposed systen.