In order to switch the dual Field of View Infrared optical system quickly,and satisfy the requirements of the portability and installation,a lightweight hybrid refractivediffractive dual FOV IR optical system is designed.The system adopts reimaging and hybrid refractivediffractive system,is optimized by optical design software,and the image quality is also evaluated.The temperature compensation is also analyzed,and the temperature compensation curves are also shown.The system can be switched from 120 mm/60 mm and the work wavelength is between 3.7～4.8 μm.The results indicate that the efficiency of the cold shield is 100%; at the Nyquist frequency 33 lp/mm of the detector,the MTF of the offaxial field is higher than 0.3,and the system’s optical length is 200 mm.The whole system consists of 7 pieces of lenses,and the dual FOV can be switched by shifting only one piece of them,which makes the system simple,lightweight with high quality imaging.