Abstract: In order to meet the requirements of low orbit spacecraft guidance, navigation and control (GNC) system for light small infrared earth sensor, the design on wide angle long-waveband infrared (LWIR) optical system and its distortion correction were studied. The wide angle LWIR optical system consists of 3 germanium lenses, using the form of retro-focus imaging, its full field of view could be 140°. The operating wavelength range is 14μm~16.25μm, and F number is 0.8. The optical system is characterized by small volume, simple structure and high image quality, the miniaturization and high-precision design of the infrared globe sensor optical system can be realized. Different distortion correction formulas were established for different field ranges, and the correction error is less than 1/5 pixel size. The distortion correction method can meet the requirement for attitude measurement of sensor products.