Abstract: The problem of thermal cavity (afterburning cylinder of a jet engine) and plume combination radiation is considered.The radiative transfer differential equation was derived.The solution of the differential equation was then obtained under the radiative boundary conditions.The detailed solution of radiative transfer equation was elaborated for a thermal cavity,filled with high temperature gas and surrounded with multiple walls of different temperatures.The detailed spectral radiant intensity expression was also given for the back hemisphere.Then a spectral radiation intensity expression was also derived for the thermal cavity-plume combination radiation.Finally a numerical example was given.Its results show that the spatial distribution of the thermal cavity-plume combination radiation has a pear shape just like that of measurements.The spectral distribution is also consistent with measurements.