The advantage of manufacturing space mirror by SiC material is analyzed, and the key technologies of fabricating and testing SiC aspheric mirror are researched. The off-axis SiC aspheric surface is ground and polished by the FSGJ-2 numerical control machine, and the contour is measured by the profilometer of FSGJ-2. For the purpose of testing aspheric mirror by null-compensation, a computer-generated holographic instrument is specifically designed and developed. Finally, an example for fabricating and measuring an off-axis aspheric mirror with the aperture of 468 mm×296 mm is given. The peak-to-valley (PV) and root mean square (RMS) values of the surface error are 0.148λ and 0.017λ (λ is 632.8 nm), respectively. It could meet the requirements of the optical design.