According to the absorption characteristics of exhaust plume, a numerical model of the infrared radiation characteristics of the exhaust plume based on Monte Carlo method is set up. Then, the infrared radiation characteristics of exhaust plumes from a engine are simulated in the five infrared 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) by this model. For verifing the rationality and reliability of the numerical simulation model, a test of the spectrum features of exhaust plume from the engine is conducted. The results suggest that there is strongest radiation of the liquid-engine exhaust plume in the band of 2.27~3.8 μm and maximum radiation area in the long-wave infrared band of 8.3~20 μm.