Abstract：With the increase of the spaceborne telescope primary mirror size，the gross weight of the whole optical system is increasing leaped. It’s in contradiction to the desire of the optical system development trends which is smaller and Lighter. In order to satisfied the development desire

the article started with the lightweighted design of the primary mirror sub-assembly structure.The influence of the material thermal math

lightweight pattern and optimal support structures was considering during the mechanical/thermal design process. In the article a higher resolution Cassegrain optical payload which primary mirror isφ650mm was designed and it’s specially support system made reflectors of the space remote sensor keep both high rigidity of structure and fine stability of thermal dimension better. Considering the telescope manufacture and work station

a reasonable and optimal structure of the primary mirror sub-assembly is taken finally

and its PV is less thanλ/10 which is satisfied to the high resolution satellite primary design requirements.