A simplified engineering model is built by analyzing the flow field of cruise missile. It can calculate the distribution of temperature and pressure if the temperature and pressure of tail pipe are known. The model is basically consistent with the simulation which is used by hydromechanics. The luminance is calculated by the C-G approximate model of spectral bands. The results indicate that the character of luminance on core area of plume is apparent and the luminance on vertical direction is brighter than other orientations. 3~5 μm spectrum band can be main spectrum band for detection for plume of cruise missile. The analysis and results provide the basis for the detection of cruise missile and selection to spectral band for spatial camera.