As to detection, recognition and simulation for infrared characteristic of target, a method based on the physical model of the targets which are irradiated through infrared illuminator is proposed. The normal circumstance and artificial infrared illuminator were combined to affect targets. The calculation model of surface temperature and infrared radiation character was built. Analysis of spectra characteristic based on carbon-silicon rod infrared illuminator, taking the Hefei’s building for example, 3~5 μm and 8~14 μm wave-band’s infrared radiation was calculated and analyzed. The results show that target’s infrared radiation character is changed when irradiated by using differential power. In the same condition, the power usage of 8~14 μm wave-band is greater than that of 3~5 μm wave-band.