In order to improve the communication quality of LEO-OGS laser links, commercial ground station telescopes equipped with large aperture primary mirrors must be able to withstand extreme outdoor temperature. A central support scheme using room-temperature vulcanizing silicone rubber was proposed for a high-precision primary mirror with an optical aperture of 500 mm. The mirror is made of microcrystal material, and both of the bushing and the supporting cylinder are made of titanium alloy. A 1-mm-thick adhesive layer is used, which can effectively reduce the thermal stress inside the assembly during temperature changes while unloading the gravity of the mirror blank. The thickness and height of the adhesive layer are determined by optimization. A specially designed fixture can accurately control the shape and thickness of the adhesive layer. The ventilation holes on the bushing promote its full solidification. Simulation analysis indicates that the surface shape accuracy of the primary mirror is 4.199 nm in RMS under 40 °C temperature variation, with 13.748 nm under vertical gravity and 4.187 nm under horizontal gravity, accompanied by the maximum mirror inclination and displacement of 4.722" and 3.597 μm, and the fundamental frequency of the assembly reaches 53.45 Hz. The measured surface shape accuracy of the primary mirror is RMS 0.017λ (λ=632.8 nm). The surface can maintain high precision after extensive heat cycling tests and vacuum coating. The central support structure can significantly improve the temperature adaptability of precise mirrors and has broad application prospects in large-scale ground optoelectronic equipment.