Abstract: To meet the requirements of large-aperture and long-focal-length star sensors, an optomechanical design of a large-aperture thermally insensitive star sensor was created. According to the index requirements, an optomechanical thermal integration analysis of the thermally insensitive system was conducted. The MSC Patran software applied temperature loads to the primary and secondary mirror structures to calculate their thermoelastic deformations. The rigid body displacement of the node after thermal deformation was calculated using the Nastran software, and the Zernike polynomial coefficients of the primary and secondary mirror surfaces after deformation were analyzed using Sigft optical mechanical interface software. The results were imported to Zemax to predict the influence of lens shape change and rigid body displacement on speckle, optical axis drift, and wave aberration. The system performance meets the index requirements and the accuracy of the optical mechanical thermal integration analysis is verified through an installation and debugging test in the temperature range of 20℃±5℃, providing an accurate and fast optical mechanical thermal integration analysis process.