To improve the fine surface figure accuracy and optical axis accuracy of an off-axis convex aspheric mirror, the fabrication and testing technologies of the off-axis convex aspheric mirror were studied. Firstly, a Three Mirror Anastigmat (TMA) optical system and the specification requirements of the second off-axis convex aspheric mirror in the TMA optical system were presented. Then, the technique of Computer-controlled Optical Surfacing(CCOS)for manufacturing the aspheric mirror and the FSGJ numerical control machine for processing aspheric surface were introduced. Finally, the contour testing in a lapping stage and the back transmission null testing in a polishing stage for the convex aspheric mirror were described, and the controlling technology for the optical axis accuracy of off-axis convex aspheric mirror was studied. The testing results indicate that the surface figure accuracy and the optical axis accuracy of the off-axis convex aspheric mirror are 0.017λ RMS and 9.4″,respectively. All the specifications of the off-axis convex aspheric mirror can meet the requirements of the optical design.