This study proposes an infrared imaging and detection model to address infrared imaging and radiation characteristics of the middle and upper atmospheric background. The applicability of the medium spectral resolution atmospheric radiation transfer mode (MODTRAN) in the infrared band is analyzed, and the strategic high-altitude radiance code (SHARC) is utilized to simulate and analyze the infrared radiation characteristics of the middle and upper atmospheric background under different observation parameters in the 3?5 μm band. Furthermore, a relevant radiation characteristic database is established to complete imaging simulation for infrared radiation scenes in the middle and upper atmospheric background. The results demonstrate that the MODTRAN in the 3?5 and 8?12 μm bands has good computational accuracy at tangent heights below 50 and 70 km, respectively; middle and upper atmospheric background radiance decreases with the increase in the tangent height and solar zenith angle, however, this increases with the observed zenith angle increase; short and long path radiation characteristics are primarily influenced by the path length and atmospheric parameters in the lower atmosphere, respectively; the radiance during the day and night reaches its global maximum at 36 and 34 km, respectively, and local maximum at 75 and 85 km. The results provide theoretical support for the infrared detection of middle and upper atmospheric backgrounds.