The characteristics of long-wavelength infrared background radiation from upper atmosphere are the important research topics for target recognition and infrared radiation characteristic measurement. According to the NRLMSIS-00 empirical atmosphere model, the influence of the temperature and gas concentration of upper atmosphere on infrared radiation is analyzed. By using SHARC, the upper atmospheric radiance code, the upper atmospheric background radiation in different observation positions and different atmospheric modes is calculated numerically and analyzed theoretically in the waveband from 6 μm to 15 μm. The result shows that the long-wavelength infrared radiation of upper atmosphere can be attenuated with the increase of limb tangent height, can be enhanced with the increase of observation zenith angle and can be attenuated with the increase of solar zenith angle. The aurora and twilight are of importance to the enhancement of the upper atmospheric long-wavelength infrared radiation and the upper atmospheric long-wavelength infrared radiation can be varied with the change of latitude and season. This analysis is of reference value to the space target sensing and infrared remote sensing.