Airborne ambient temperature varies widely and airborne vibration can be strong. Because there is a difference in the thermal expansion coefficients of an Invar inlay and mirror material, a mirror’s higher coating temperature means that the traditional bonding process will lead to bonding failure and the surface precision of the mirror cannot meet system requirements. Therefore, this paper proposes a new method of bonding the mirror after processing and coating, and designs some important parameters for the adhesive layer. RTV is used as the main binder for the mirror and the inlay, and the effect of RTV curing on the structure is alleviated by favorable elasticity. The thickness of RTV is 1.1 mm, its width is 7.2 mm and the thickness of the epoxy adhesive is 0.022 mm. The simulation results show that the RMS of the mirror shape is 25.91 nm and the first-order frequency of the mirror group mode is 242 Hz when the gravity is 1 g and temperature change are -40 °C (the initial temperature is 20 °C). The final surface detection RMS is 15.8 nm and the resonance frequency is 213 Hz. The experimental results show that the design, structure and bonding layer can meet the wide temperature range and vibration requirements.