Abstract: The problem that the primary mirror center is obscured by secondary mirror, existing in the reflective optical system, is researched for designing an optical system of the high-resolution space camera. Three optical systems of half, full and annular FOVs were proposed based on the analysis of the structural parameters of the coaxial three-mirror-anastigmat system and the distribution of the final FOV on the image plane. The coaxial three-mirroranastigmat systems of three modes, whose focal length is 3000 mm and F number is 10, are designed. The result indicates that the image quality of the three optical systems approaches the diffraction limit in the effective field, and can meet the different demand of high-resolution space camera. It is pointed out that the coaxial three-mirror-anastigmat system with half FOV is suitable to the push-broom imaging of linear array CCD, the coaxial three-mirror-anastigmat system with full FOV can be used to the staring imaging of planar array CCD, and the coaxial three-mirror-anastigmat system with annular FOV can realize the full color and multispectral imaging on a same camera.