The simulation of CO2 laser illumination on explosives was implemented. The three-dimensional models are built for the study of radiation temperature variation of the target surface during process of laser illumination and cooling down in 8~14 μm and 3~5 μm waveband. The target with explosive residues are observed with the thermal imaging equipment(8~14 μm and 3~5 μm). The studies show that the radiation temperatures of TNT and substrates are determined by the emissivity and reflectivity in process of laser illumination in 8~14 waveband. The radiation temperatures of TNT and substrates are determined by the emissivity in 3~5 μm. In the illumination process, the radiation temperature of TNT areas is higher than surrounding areas in 8~14 μm waveband. In 3~5 μm, the radiation temperature of target surface has decreased instantly, and the radiation temperature of stained areas is lower than surrounding areas.