Finite element models were established for both conventional bolts and thermally adapted bolts to discuss the thermal mismatch issue between high-temperature alloy bolts and C/SiC plates, The variations in bolt preload under high-temperature conditions were compared, and the effects of interface friction and dimensional deviations on the thermally adapted bolt's performance to maintain preload were analyzed. The results indicate that thermally adapted bolts exhibit superior preload retention performance compared to conventional bolts. The presence of interface friction significantly impacts their connection performance: under frictionless conditions, the preload remains nearly constant, while in the presence of friction, the preload first decreases and then stabilizes as temperature increases. Regarding dimensional deviations in the bolt head's maximum radius or the thickness of the material washer, under frictionless conditions, the remaining preload of the bolt linearly changes with temperature—decreasing linearly when dimensions are larger than the designed and increasing linearly when dimensions are smaller. When friction is present, the remaining preload initially decreases with rising temperature but subsequently follows the same trend as observed under frictionless conditions.