Exhaust plumes of solid rocket motors involve complex flow state, afterburning and radiation effects, which have an important role in the operations of detecting, indentifying, and tracking. To investigate the characteristics of afterburning and radiation effects under different flight conditions, the computational fluid dynamics method and the finite-rate ratio model were used to simulate the flow properties with chemical reactions, and line of sight method was utilized to solve the radiation transmission equations. The influence of afterburning effect on the radiation characteristics of different heights was analyzed. The results show that the afterburning effect can cause the flame temperature rise to 1 000 K, and increase the radiation brightness of the flame band more than 10 times. For different bands, the radiation brightness rises and then decreases along with the height. The maximal position is 20-30 km, with about 17 times radiation enhancement in the short wave 2.7 μm waveband and about 16 times in the 4.3 μm mid wave waveband. It can be seen that the contribution of the H2O molecule caused by the afterburning is greater than that of the CO2 molecule. Theses can provide reference for further theoretical research and engineering application.