Traditional infrared detection distance model is mainly used for ground target detection, and the flying height of the carrier aircraft is relatively low.Based on analysis to staring infrared thermal detectors, the near space environment was studied and a background radiation model was established.Based on which, an infrared detection distance model of near space aerocraft was proposed, and the application range of infrared bands was discussed.The results show that:1) in the near space environment, infrared band has better detection results; and 2) in the detection using shortwave, the background radiation has a great effect on the detection results.