In order to achieve the long-wave infrared hyperspectral imaging for remote sensing target and to meet the needs of target detection for large amount of information, a long-wave infrared (8~12 μm) imaging spectrometer with high spectral resolution is designed. Off-axis three-mirror system is used in fore telescope system to implement a design of no obscuration, large diameter and wide-viewing-field imaging. The refraction and reflection structure is respectively used in optimizing the spectrophotometric system. The result shows that the optical system with an aperture of 100 mm, F number of 2, spectral resolution of 16 nm, spatial resolution of 150 μrad, cold aperture efficiency of 100% and image quality closing to the diffraction limit can be designed using refractive structure. However, when reflective structure is adopted, multi-chip off-axis mirrors are used to ensure that the optical system has no obscuration, which results in an increase of the asymmetry of the system and makes it difficult to correct the astigmatism, coma and field curvature to the best condition. The design result shows that hybrid refractive and reflective imaging spectrometer has the advantages of high spectral resolution, good image quality, reasonable structure and the match between the root-mean-square (RMS) diameter of point spot and the pixel size of the existing domestic detectors.