In order to sovle design difficulties about failure of opto-mechanical system features due to axial pre-loading caused by thermal deformation, a controlled design method with axial conformity for opto-mechanical structure is proposed. The relationship between the thermal deformation and axial pre-loading is got based on the analysis of the thermal effect model. By comparing with the thermal analysis in the conventional axial pressure structure, a flexible element with controllable conformity between the axial pre-load and the thermal deformation is designed. The deformation analysis of the flexible elements with various model parameters showed that there is controllable conformity for the axial thermal deformation when the temperature is changed. A practice design method is given to built a model to calculate the axial thermal deformation and parameters for the flexible element. The controlled design method of axial conformity is used to design the construction of the star simulator. The measured results reveal that the method is feasible and effective.