针对12 m轻量化SiC主镜，提出了轴向支撑采用18点Whiffle-tree结构结合压杆结构，侧向支撑采用A-Frame柔性机构结合切向支撑机构的支撑方案。从原理上对该主镜支撑方案进行了分析，说明了采用以上两种结构的优点；通过有限元方法对各个机构参数进行了分析、优化，并对整体结构进行了静力学以及热学仿真。实验显示：在参考温度下主镜面形精度(RMS)值为35 nm；温差达到40 ℃时，RMS值为111 nm。该设计方案满足了12 m轻量化SiC主镜的支撑要求，同时可以很好地抵消热应力对主镜的影响。

A design based on 1.2 m lightweight SiC primary mirror is presented. An 18 point Whiffle-tree structure and a pressure bar are used for the axial support, and an A-Frame flexure mechanism and a tangent link are used for the lateral supporting system. The project of primary mirror design is disscussed in the principle, and the advantages are given. The parameters of mechanism are analyzed and optimized by the Finite Element Analysis(FEA) method. The whole FEA model is established, and the statics and thermal simulation analysis are accomplished. Experiments indicate that the Root Mean Square(RMS) of the mirror resulted from the supporting system is 35 nm at reference temperature, and it is 111 nm when the temperature difference is 40 ℃. The results show that the design could suit for the 12 m lightweight SiC mirror well, and thermal effect could be compensated successfully.