Abstract: The large-angle and lateral infrared radiation behind the aircraft are increasingly becoming detection targets of the enemy. Reducing the infrared radiation characteristics of the plume in the 3–5 μm bands is an effective way to improve the infrared suppression effect within the corresponding range. In this study, the effects of installing a radiant plate in an axisymmetric convergent nozzle on reducing the plume temperature and suppressing infrared radiation were investigated. In this study, the changes in the heat transfer and infrared radiation characteristics of the nozzle were studied before and after installation of the cross-radiant plate under Ma=0.8. The results indicated that the introduction of a radiant plate can shorten the length of the high-temperature region of the plume. At Ma=0.8, the infrared radiation intensity of the plume in the 90° direction decreased by 11.31%. This study further explains this phenomenon from the perspective of the coupling effect of convective heat transfer and thermal radiation.