A flexible supporting structure composed of 3 Bipods was designed to enhance the surface accuracy of a minitype reflector in complex environments. Firstly, the flexibility matrixes of the Bipods and whole support structure were established through matrix transformation and the defining design variables of the Bipods were optimized through MATLAB to meet the requirements of maximum of the axial stiffness when the radial stiffness was minimum. The simulation verification was then performed by applying different forces and thermal loads to the optimized supporting structure. Finally, a zygo interferometer was employed to verify the thermal stability of the supporting structure. The results show that the Bipod support structure keeps a fine surface accuracy under a thermal-structural load, meanwhile providing excellent dynamic performance. Except for giving the reflector a better thermal stability, the support rigidity of the structure resists the impact of the environmental dynamic load on the reflector. Moreover, the analysis indicates that the first order natural frequency of the flexible supporting structure is 1 781.7 Hz, and the relative error is 1% as compared with that of the theoretical calculation.