Now the design and fabrication technology of large aperture SiC mirror assembly is the key point during the process of lightweight of the camera. The design process of a large aperture SiC mirror assembly is shown, which is the key structure of a lightweight camera, and a main flowchart of design techniques of a highly reliable, efficient and reasonable large aperture mirror assembly is given from the aspects of the principle prototype design, dynamic prototype design and ground test. Experimental results indicate that the 1st natural frequency of the SiC mirror assembly is 340Hz .There is 8.5% difference between the Finite Element Analysis (FEM) analysis results and the experimental results. At the same time，the difference of the mirror synthesis face figure error RMS was 0.009λ before and after the vibration experiment. All the experimental results show that the SiC mirror assembly satisfies the requirements of lightweight camera very well. Moreover, the design technology flowchart of the SiC mirror assembly is adaptive to the other large aperture mirror assembly design process. The result shows that it is a good method to improve the reliability of the large aperture mirror assembly and shorten the development periods.