A novel flexible support structure for the 1-m primary mirror of a space camera was introduced. By taking the material selection, diameter-thickness ratio, number and positions of support points, and lightweight forms as design variables and the surface figure accuracy rms of the mirror under the self-weight as objective function, a kind of back opening SiC space mirror with triangle lightweight holes and three-point support on the back was designed optimally. Then, the flexible support structure was designed for the primary mirror. Through sensitivity analysis, the parameters of flexible support structure that effect on rms of mirror were found when its optical axis was on the horizontal state. By using finite element method, the dynamic and static stiffnesses as well as thermal character of the primary mirror subassembly were analyzed. The results indicate that surface accuracy of the mirror has reached rms 5.6 nm and 2.7 nm under gravity perpendicular to optical axis and a uniform temperature rise of 4 ℃, respectively, and the fundamental frequency of the primary mirror subassembly is 192 Hz. Finally, dynamics test was performed in the laboratory, experimental results indicate that the first-order natural frequency is 197 Hz and the maximum stress is 181 MPa, which verifies the accuracy of FEA. Obtained results satisfy the requirements of space application.