Abstract: In order to overcome the difficulty of manufacturing off -axis aspheric surface, the key technologies of fabricating and testing SiC aspheric mirror especially for off-axis asphere with abnormal shape were studied. The off -axis SiC aspheric surface was grinded and polished by DMG, FSGJ -2 numerical control machine and IBF, the contour and optical parameters were measured and controlled by the coordinate measuring machine and laser tracker. Finally, an example for fabricating and measuring a similar eight-square off-axis aspheric mirror with the aperture of 600 mm270 mm was given. For the purpose of testing the aspheric mirror by interferometry, a null lens compensator was specifically designed and developed. As results, the peak-to-valley (PV) and root mean square (RMS) values of the surface error are 0.219 and 0.018 (is 632.8 nm), respectively.