Abstract: To decrease the addition wavefront of large aperture mirror caused by gravity influence on beam quality in inertial confinement fusion facility, the back support technology is researched in this paper. By support structure optimization, the addition wave front caused by gravity of large aperture decreases from 0.5 micron to 0.26 micron. In this paper, the drill and the join technology of the mirror and support structure and the mirror support structure is researched and the prototype is developed to validate the technology. The test indicates that the wavefront of the mirror caused by the drill and join technology can be ignored and the mirror support structure can satisfy the mirror requirement. The addition wavefront caused by gravity can be well controlled by mirror back support technology.