In order to increase the high resolution detection capabilities of zoom optical system in a complex environment, and to solve the problems of the slow conversion speed of the optical path and differences among the object information of different bands in the multi-band optical system, a visible (0.38～0.76 μm) and middle infrared (3～5 μm) continuous co-caliber common zoom optical system with working focal length of 7.52~98.35 mm and zoom ratio of 13×was designed . The zoom ratio variation of visible and middle infrared at any zoom position was analyzed based on the positive compensation zoom group theory. The three thin achromatic lens focal length compensation theory and dual-band expression were derived. The power of zoom group and compensation group were matched rationally, making the system have the same zoom ratio at any zoom position and focal length, which improved consistency of dual-band target information. According to requirements, the dual-band athermal optical system with the temperature of －40~+60℃ was designed with the use of optical passive. The results show that the system has compact structure, fast response and good overall image quality, which can achieve all-weather day and night work.