The surface figure precision of the primary mirror in a large aperture telescope is a key factor influencing the imaging quality. In the opto-electronic system, the axis support point’s position of the primary mirror is important for the mirror surface figure error. Whether the axis supports points position is appropriate will affect image quality in some degree. We research the axis support and radius support techniques of a large-aperture telescope primary mirror in detail. With finite element method software ANSYS, the primary mirror parameter model is built. We introduce how to decide the number of the different aperture mirror axis support points. The position of the different aperture mirror axis support points is optimized and the best position of support point is provided. The optimized analysis results indicate that the mirror surface figure error is satisfied. The surface figure is mostly influenced by the axial support system.