With the continuous development of optical technology in recent years, the pace of human exploration of space has further accelerated. Space remote sensing technology is widely used in surveying and mapping, environmental monitoring and other fields. Therefore, the requirements for space optics technology are gradually increasing. In order to reduce the launch cost and the deformation of the supporting member and the main mirror base under its own gravity, a lightweight design must be carried out. Therefore, under the premise of ensuring the rigid body displacement of the mirror body and the error of the mirror shape, lightweight has become a key requirement for the development of remote sensing technology. By comparing various supporting structures, the spatial freedom of the mirror is calculated. Choose a combination of 9-point post-support and 3-point peripheral support. Compare and select the materials commonly used in the structure of the supporting part and the main mirror base. Although the support structure adopts topology optimization, a very effective support method can be obtained, but the final result cannot be universally applied to the support structure of mirrors with different apertures. Therefore, this paper determines the design structure of the relationship between the mirror support position, the fundamental frequency and the surface shape accuracy and the support structure parameters based on the flexibility matrix. For the rigid parts of the supporting structure and the main mirror base, simulation software was used to optimize the design of the initial design structure to remove excess materials. The final main mirror base lightweight rate was 36.6%, and the triangular plate lightweight rate was 65.9%. The static analysis and modal analysis of the supporting scheme are carried out by analysis software. After optimization, the shape accuracy of the primary mirror under its own weight is better than λ/50. Structural resonance will seriously affect the use and life of the equipment. Therefore, the modal analysis is performed, and the fundamental frequency is within a reasonable range during the optimization process. The simulation results show that the first-order fundamental frequency is 836.55 Hz. The analysis results show that while ensuring the shape accuracy of the primary mirror, the lightweight design of the mirror support assembly is realized.