In consideration of the serious chromatic aberration and lower energy transmittance of a multi-band infrared MWIR/LWIR(Medium Wave Infrared/Long Wave Infrared) dual-FOV(Field of View) common-path optical system, a dual-FOV and dual-band common-path refraction optical system is designed to implement the multi functions of the imaging system. The system is based on a cold 320 pixel×240 pixel MWIR/LWIR dual-band staring focal plane array detector and introduces aspherical optical components to improve its aberration correction ability to adjust the align structure of lenses. The optical system is made up of a zoom subsystem and a secondary imaging subsystem with a 50 mm focal length and a 200 mm focal length and satisfies 100% cold shield efficiency. The image evolution shows that the Modulation Transfer Function(MTF)of LWIR and MWIR is almost reaching the limit of diffraction and greater than 0.5 respectively at the spatial frequency of 17 lp/mm, and almost 80% of the energy is concentrated at one pixel. In addition, there is no obvious cold reflect phenomena observed, and the optical system has a preferable application foreground in military and civilian opto-electronic detective fields for its wide scopes of application, compact structure, small volume and good imaging.