As the most important main support structure of a space telescope, the cylindrical mirror barrel structure accounts for a relatively large proportion of the mass. Due to the larger number of lens groups and larger system aperture, the system is heavier and larger in size, which needs to be structurally lightened; In addition, the cylindrical lens barrel structure needs to focus on the impact of the structure on the performance of the entire optical system. In addition to considering the specific structural properties such as strength and stiffness, the cylindrical lens structure also needs to focus on the impact of the structure on the various performance indexes of the optical lens as well as the impact on the performance of the entire optical system. Therefore, in order to design the mirror cylinder structure with reasonable structural form, high lightweighting rate and high stiffness, it is necessary to optimize its design.First, based on an empirical structural design approach, the primary support structure of the large- aperture refractive space telescope was designed, and a finite element model was established. The finite element analysis method was used to perform topology optimization on the cylindrical mirror barrel structure, resulting in a reasonable optimized structural model. Then, dimensional optimization was performed to determine the optimal structural parameters. Afterward, the optimized mirror barrel model was reconstructed. Based on the optimization results, static and dynamic analyses were conducted to evaluate the surface shape indices of the lenses, the safety factors of each structure and lens, and to assess the overall system performance and safety. Finally, experimental testing was carried out on the large-aperture refractive space telescope to verify whether the structural performance of the optimized design met the design requirements.After the optimization design, under the influence of axial gravity, the maximum displacement of the large-aperture refractive space telescope was 6.719 μm; Under the 5 ℃ temperature rise loading condition, the maximum deformation was 6.697 μm. These deformation values are relatively small, indicating that the large-aperture refractive space telescope can meet the displacement and deformation requirements under static loading conditions. The displacement and deformation parameters of each lens were fitted under static conditions to obtain the surface shape indices of each lens. Taking the surface shape index of the large-aperture lens 10 as an example, under the 5 ℃ temperature rise (with a reference temperature of 20 ℃) and axial gravity coupling condition, the maximum peak-to-valley (PV) value of the large-aperture lens surface was 9.62 nm, and the maximum root mean square (RMS) value was 2.21 nm. These values satisfy the design requirements of PV<λ/10 and RMS<λ/50 (λ=632.8 nm). Under dynamic loading conditions, the first-order fundamental frequency of the mirror barrel structure increased to 2871 Hz, significantly improving its structural stiffness. The overall mass was reduced from the original 3.022 kg to 1.053 kg, achieving a 65.16% reduction in weight, resulting in a more rational lightweight structural form. The fundamental frequency of the entire system was 2074 Hz, which is well above the required system fundamental frequency (not lower than 150 Hz), ensuring that there will be no resonance with the carrier.The lens assembly was machined using optical centering processes. The lens group was installed onto a centering lathe with the help of a specialized fixture, and the optical axis of the lens group was aligned with the lathe's main spindle using a centering instrument. Afterward, precision turning was performed on the lens group to meet the design requirements. The mirror barrel was processed using casting, turning, and other methods, followed by blackening or stray light elimination treatments. Finally, the lens assembly was placed into the mirror barrel. After assembly and adjustment, the system was tested using a ZYGO interferometer. The test results showed that the system wavefront aberration of the large-aperture refractive space telescope was 0.124λ, which is less than the design requirement of 0.15λ, indicating good imaging quality and validating the effectiveness of the structural optimization. The optimization design method used in this paper can provide valuable reference and guidance for the optimization design of similar optomechanical structures.