The effect of background radiation, such as the sunshine, the atmosphere and the ground on the total infrared radiation signature of a subsonic aircraft was studied by using the infrared radiation signature computation model under typical background environment. The influence of the background radiation on the infrared suppression of low emissivity was analyzed. The results show that the sunshine radiation has a great effect on the front detection region of the aircraft in the 3-5 μm waveband; the atmosphere and ground radiation has a more obvious effect on the front and side detection region of the aircraft in the 8-14 μm waveband; the impact is different when the detection orientation and season changes; the infrared radiation suppression effect of low emissivity is reduced or even failed because of the background infrared radiation reflected from the skin.