Abstract: According to the design requirement of the 400 mm-aperture tracing telescope, one effective structure was introduced. Firstly, the telescopic structural style and system parameters were determined, and the whole system was divided into several main constituents. Secondly, the structure of the primary mirror cell was emphatically fixed, and the support structure of the primary mirror was determined according to the optimization of the best support positions, and the structures of the secondary mirror support and three-beam were designed. Thirdly, with method of finite element model and analysis, the primary mirror surface figures caused by the gravity and temperature change were intensively studied, and the stiffness of the whole telescopic system and the contribution of the primary mirror and secondary mirror separation caused by the change of temperature were analyzed. The mirror surface figure RMS was less than 0.033 wavelength in the ultimate state and the stiffness and temperature adaptability of the whole system were assured. The analysis results indicate that the design requirement of the mirror support structure and the whole system are achieved, and the direction for similar structure is provided here.