A scanning mirror with the material RB-SiC was designed based on the flexible support, which could operate in complex environment and the reflection mirror′s surface precision was enhanced. A lightweight design was conducted on the scanning mirror in the way of combining the triangular elements and quadrilateral elements on the back-open-architecture; The locations of supporting were optimized by analyzing the impaction of supporting span on the deformation of mirror. Meanwhile, the universal-flexible support structure was designed to eliminate stress during alignment process and alteration of environment. The finite element model of the scanning mirror component was established, and the surface precision could be 0.023λ according to the calculation; The mirror′s surface precision was measured by the ZyGo interferometer with the method of autocollimation after calculation, and the RMS was 0.029λ. The static and dynamic imaging tests were compared through the simulation of the infinite distance target, and the results show the image quality meets well. The imaging stability of the scanning mirror performs well after flight test of imaging the target on ground, the result shows that the photograph performs well.