Abstract: Based on a space optical system launch mission, the supporting radius of the 2 m primary mirror of the optical system subject to axial 1 g inertial load was optimized to achieve the minimum surface deformation. Taking surface error of the primary mirror as objective function and force actuator inputs as design variables, a mathematical model coupling finite element analysis and optimization algorithms was build. The optimum force actuator inputs of the primary mirror were investigated with the optimization model under axial 1 g inertial load condition and axial 1 g inertial load coupled with 1℃ temperature load condition, and the surface RMS of the primary mirror with optimum force actuator inputs are 19 nm and 43 nm respectively. It shows that the optimization method of primary mirror with active supporting system discussed in this paper is applicable.