Abstract: The detection range of infrared system depends on its dynamic characteristic, the radiation of target and background, the atmospheric attenuation and so on. Aimed at the flying projectile’s relative radiation received by the infrared system, a new detection range model of infrared system was proposed. It considered the equivalent area radiation of the projectile and the equivalent background radiation around the projectile and atmospheric attenuation. Based on analysis of infrared radiation on the surface of projectile, a new calculation equation for detection range was derived and analyzed.