It is a difficult problem to evaluate the signal parameters of optical radiation characteristics of solid propellant. The research proposes a multispectral evaluation method of propellants radiation signature index (PRSI). The infrared radiation intensity, ultraviolet radiation intensity and visible radiation intensity of both HTPB composite propellant and nitrocellulose propellant were tested with infrared radiometer and ultraviolet and visible light radiation measuring instrument, and then used the method of PRSI to compare the test results. The results show that the PRSI values of UV and visible light produced by the combustion of HTPB composite propellants are significantly larger than those of the nitrocellulose propellants. The multispectral exponential factor evaluation method based on the inherent parameters of propellants, such as mass-combustion heat and burning velocity, can not only compare the difference of spectral characteristics of similar propellants, but also compare different types of propellants.