The harsh airborne environment has put forward high requirements for the long focal common-aperture optical system. Four key technologies are studied, reasonable and feasible solutions are given. The design of the multi-spectral common-aperture optical system developed enables the airborne optical imaging system to meet the requirements of miniaturization and lightweight. In the range of airborne ambient temperature variation, the high-gradient silicon carbide aspheric surface optical processing and detection method proposed ensures that the radius of curvature and the accuracy of surface shape of optical elements remain stable and can achieve excellent imaging quality. The application of silicon carbide reflector flexible support technology enables the optical elements and support structure to have higher structural strength and stiffness, and at the same time can ensure the dimensional stability of the optical system structure. The wavefront of the actual optical system carries a lot of errors. In this paper, the computer-aided precision mounting technology is proposed to implement the mounting of the optical system with high image quality.