Infrared radiation characteristics of the high-temperature H2O and CO2 gas mixture jet flows are investigated with the numerical simulation method. The infrared band is divided into five bands (1.32-1.69 μm, 1.56-2.27 μm, 2.27-3.8 μm, 3.8-8.3 μm and 8.3-20 μm) according to the absorption features of H2O and CO2 gases. The model for describing the infrared radiation characteristics of wake flows from an engine nozzle is set up, and the radiation characteristic distributions of jet flows in the five infrared bands are numerically simulated based on this model. The results show that the more H2O content in the jet flows, the more contributions to the energy diffusion, thereby the temperature of jet flows and the quantity of radiation are lower. In addition, there is the maximum radiation quantity in the mid-wave infrared band and the minimum radiation quantity in the long wave infrared band.