Abstract: The hyperspectral imaging spectrometer is a new type of load in the modern space remote sensor. The hyperspectral imaging spectrometer optical system designed in this paper has been made up by two parts, front telescope system and imaging spectrometer system. The front telescope system and imaging spectrometer was designed respectively, then assembled and optimized. Off-axis TMA structure was used by front telescope system to increase width, improve image quality, and reduce distortion. Separated fields method was applied on front telescope system for larger swath width and better image quality. Imaging spectrometer was designed by Offner structure with grating convex second mirror. Assembled system has larger swath width, smaller volume, better image quality, higher spectral resolution, and more spectral passage. The MTF of every fields and every spectrum is higher than 0.7 at Nyquist frequency, the diffusion circle of image with 80% energy is 15 m, smaller than CCD pixel size, so the image quality reaches the technology target of system.