As the mismatch of thermal expansion coefficients between the lens and the frames,stress on the lens is brought under the large temperature range,which can affect the properties of optical system.So a special support structure is designed to minimize the stress.Firstly,several existing form of surface contacted are analyzed and compared,then the axial and radial effect caused by temperature is calculated,and the fixing and orientation structure is designed prettily.Lastly,the impact of reducing the thermal stress is simulated by the MSC.Patran software.The result indicates that the space and pad for reducing the thermal stress make the stress and deformation of lens caused by temperature decrease clearly,and the rigidity of the assembly system is fine,assembly method simple,as a broad applicable design method can solve the support structure of coaxial optical system.