The rectangular mirror supporting structure was designed and optimized for reducing the weight of the aerial optical remote sensor and minishing the shape error of the mirror, which was working in the bad aerial environment. First, the supporting point number of the ligntweighted mirror was calculated and the point position was optimized. Secondly, the flexible hinge was designed and optimized in the supporting structure in terms of the thermal deformation, which was indeced by the different expansion coefficients between the mirror and the back supporting structure. Finally, the surface shape was analyzed, the RMS was 20.3 nm, less than the design requirements, 1/30λ(λ=632.8 nm), the model was analyzed and tested, the first-order natural frequence was 138 Hz and 162 Hz. The results indicate that the designed structure is resonnable and feasible.