In order to improve long range infrared target detection and recognition,besides the traditional measures such as increasing the focal length and effective aperture,it is necessary to further obtain the multi spectral information of the target,so as to distinguish the target with different radiation characteristics from the background.In this paper,a multispectral infrared detector and prism rotating image shift imaging optical system is proposed.The infrared radiation energy of the same target is converged to different spectral regions of the detector for imaging,thus obtain multispectral imaging information of the same target.The system adopts coaxial reflective optics,which has two infrared detectors with 8 different spectral sections.The information of 8 spectral sections of the same target can be obtained by prism rotation.The focal length of the system is 520mm,the effective aperture is 200mm,and the F number is 2.6.The optical structure of the system is compact,the prism rotation corresponds to the detector imaging in real time,there is no imaging delay and image rotation,and it has the characteristics of large aperture,long focal length,multiple spectral segments,etc.,which meets the system requirements of high resolution,long operating distance and multi spectral information acquisition.