Abstract: The long-circular mirror were optimized with the finite element technology. It could reduce the mass of reflector in space optical remote sensor and minish shape error of the mirror, which was running in the bad environment of the space. Firstly, the reflector was lightweighted and optimized in terms of supports location and structural topology. Secondly, the flexible support was optimized. A new flexible hinge was stated out. The radial deformation was usually not matched between mirror and its backplane because of different coefficients of expansion. The problem was solved with flexible support and the mirror shape accuracy was improved. The maximum value of RMS error, 14.6 nm, was less than the design requirements,/30 (=632.8 nm). The first -order natural frequency is bigger than 100 Hz which shows that the optimization design method is reasonable and feasible.