Aiming at the extremely high optical path stability requirements of the spatial gravitational wave telescope in the order of picometer, the main mirror components in the system were optimized. Zerodur was chosen as the material of the primary mirror, the support structure was Invar. Firstly, through the optimization of the parameters of the mirror analysis, while ensuring the accuracy of the surface, the mirror light weight rate reached 72%. Then a biaxial joint Bipod flexible mirror support structure was designed, using the side of the three-point support form. In order to ensure the effective support stiffness and unloading effect, the mathematical model of the mechanism was established, and its size parameters were optimized based on Matlab. Finally, the modal analysis and vibration test of the primary mirror components were optimized, and the on-orbit analysis and wavefront quality calculation were completed. The results show that the first-order natural frequency of the primary mirror component is 373 Hz, and the relative error of the test result is 3.5%. The main mirror accuracy is 8.9 nm(RMS); wavefront accuracy is ?姿/5(?姿=1 064 nm). The analysis results show that the reflector assembly meets the design requirements.