The paper aims at obtaining the optimum lightweight configuration for a 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 were 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 launch accelerations. The optimum lightweight M1 with a MRR of 0.5 and a mass of 9.72 kg is attained and a mirror blank based on this design was manufactured. The performance of the optimum lightweight mirror is simulated and the simulation results satisfy the requirements of space specifications.