Abstract: Image quality of large aperture infrared optical system is easily suffered from ambient temperature and deadweight, which can be solved by infrared adaptive system. Infrared adaptive optical system based on Hartmann-Shack wave-front sensor is designed in this paper. Large aperture telescope engaged in dual waveband such as middle-infrared wavelength and visual wavelength is designed to have 10^× collimation with optical configuration of reflective Cassegrain objective lens group and multispectral achromatic refractive eyepiece lens group. Relay infrared objective lens is designed to compensate aberration of infrared telescope. Reimaging optics is chosen in such a way to minimize objective lens while maintaining 100% cold shield efficiency. Thus MTF of dual-waveband optical system for IR adaptive system can approach diffraction limit(more than 0.5). Image quality can meet technical requirements.