binary optics can be used to increase optical performances, decrease size and weight, and decrease systems costs in numerous applications. by means of hybrid diffractive-refractive, a switch-zoom optical system of catadioptric large aperture ground-based photoelectric detection is designed. the characteristic of the system is that it is a compact optical system without moving parts which can get two focal lengths. and the quality of image approaches the diffraction limited. ritchey-chrtien (r-c) mirror and a field lens are common for long-focus system and short-focus system. two refract groups transmitting optical system are used for zooming. in order to satisfy the demand of energy regulation, it is designed afocal beam between field lens and later refract optical system. filter and variable density plate are placed in it to guarantee the imaging quality. the focal length is 3750mm and f number is 7.5 for the long-focus system, and the focal length is 1850mm and f number is 3.75 for the short-focus system. former part and later lens of the system are both perfect imaging. they can be fabricated and detected independently. so the design demand can be satisfied better and the imaging quality can be improved.