The mirror assembly of an electro-optical tracking and pointing system for a space borne laser communication system is studied, three flexible supports are contrasted, according to practical applications of space load, the structural stiffness advantage and surface figure of the three flexible support scheme have been evaluated. The analysis results show that the surface figure RMS of neck side grooving flexible support scheme resisting micro- gravity and thermal environment change can reach 2.05 nm and 8.88 nm, the fundamental frequency mode is 926.1 Hz, in the balance between the surface figure RMS and the higher stiffness resisting hevibration damage, the flexible design is most reasonable. On this basis, the parameterized design of the flexible support structure of the reflector is completed and dynamic analysis have been done. The maximum stress of the frequency response is 96 Mpa, which is less than the material’s tensile strength limit. The results of random vibration analysis show that root mean square of acceleration response is 11.14 g RMS, meeting 3σ law. Finally, a 0.2 g sine sweeptest proves that the relative error of the modal analysis is 2%, the experimental result show that the analysis results are basically accurate and reliable, that is, flexible support design is reliable to meet the requirements of use.