To improve performance of a large area high resolution optical system, a novel infrared diffractive-refractive hybrid system in 8~12 μm with 16° FOV is designed based on the thermal properties of the diffractive lens and the theory of athermalization. The effective focal length and back working distance of the system are respectively 100 mm and 133 mm,while the F number is 1.9. The system is composed of three lenses, which used only two materials of Ge and ZnSe, including a conic surface and a diffractive surface.The results show that the hybrid system possesses better athermal performances and high image quality in －30 ℃~70 ℃.Additionally, the system has a compact structure, lightweight, which make the system can satisfy the necessary specifications of modern optical instruments.