The paper is aimed at obtaining the optimum lightweight configuration of the primary mirror (M1) with honeycomb patterns for a space satellite. The finite element analysis and Zernike polynomial fitting based on the Taguchi Method are applied to the whole optimization process. Geometrical control factors and levels have been selected to minimize the ratio of various mass reduction ratios (MRRs) to the product of the corresponding maximum mirror structural deflection and optical surface peak-to-valley wavefront aberrations under launching accelerations. The optimum lightweight M1 with a MRR of 0.5 and a weight of 9.72 kg is attained and the mirror blank based on the design has been manufactured. In addition, the optimum lightweight mirror is verified computationally to pass through the mechanical requirements of space specifications.