A dual-FOV conformal optical system is introduced.Zoom theory is applied in this system with a conformal window.Secondary imaging optics configuration and axial motion are adopted in this optical system.The conformal optical system is developed based on a ellipsoid surface window,whose F/ # is 4,zoom ratio is 3∶1，and operating wavelength is 3.7～4.8 μm.The high image quality and 100% cold stop efficiency is achieved.