In terms of the strict design requirements of Ф1.05 m primary mirrors for space optical systems, a new method of structural optimization design of lightweight mirrors is proposed, and a platform for automatic simulation analysis and optimization design of mirror structures are established. The primary mirror design with excellent performances is determined based on that platform. The primary mirror weighs less than 50 kg, and the lightweight ratio is close to the foreign advanced level. The first mode frequency of the primary mirror under the support of three spherical hinges is 361.2 Hz, and the first-order non-zero free modal frequency is 501.9 Hz. Under the uniform temperature change of 1 ℃, the surface figures with defocus and without defocus are 0.55 nm RMS and 0.10 nm RMS, respectively. The maximum stress of the primary mirror under 30g overload acceleration is 16.1 MPa. All of these performances meet the design requirements. The most advanced third-generation large-aperture mirror processing technology is adopted, and the route is ultra-precision milling, CNC grinding and polishing of small grinding head, and ion beam finishing. In order to ensure the consistency of surface shape test results no matter in the space or on the ground, the gravity unloading technology, and surface shape error data post-processing technology are developed to eliminate the influence of gravity and other systematic errors. The final surface shape accuracy of the primary mirror reaches 0.011 λ RMS, which shows a high precision optical surface and demonstrates the rationality of the scheme.