The radiation effect of reaction control system’s hot gas jet has an important role in optical detecting and tracking operations. Based on spectral band radiation model, and by solving three-dimensional Navier-Stokes equations with chemical reaction source term and radiation transport equation, numerical simulation of hypersonic vehicle’s RCS hot jet interaction flow field and its infrared radiation characteristics is performed, the influence of afterburning effect, flight condition and observation angles on radiation characteristics is studied. The result shows: Computational results compare well with experiment results in typical condition, which indicates the flow field and radiation computation method has good adaptability; Infrared radiation in flow field is mainly contributed by CO₂ and H₂O, where CO₂ contributes more, afterburning effect has significant influence on flow field radiant intensity, it can increase the flow field radiant intensity more than double at an altitude of 20 km; Flow field radiant intensity first decreases and then increases as flight velocity/altitude increases, as flight altitude increases, the influence of afterburning effect on radiant intensity sharply diminishes; The radiance enhancement caused by vehicle’s RCS plume is apparent, the radiant intensity at top view and 3-5 μm band is the strongest. These results can provide reference for further application in aircraft detecting and tracking.