To accomplish the real-time track and measurement of remote distance objects, a continuous zoom optical system with an aperture of 650 mm and the long focuses of 5 000—2 000 mm was designed. The combinatorial design method of a Newton catadioptric system and a reverse continuous zoom system was adopted, and the pupil was matched and connected reasonably. A proper pupil position was determined, then, the ghost often appeared in the image plane in zoom process was eliminated. By reasonable matching the focal power of the main system and the zoom system, the secondary spectrum was minimized. By using the CODE Ⅴ software to optimize and balance the aberration of every focal length, all the aberration of focal positions in the zoom optical system were corrected and balanced, and the image plane was consistency strictly. Thus, the imaging quality of each focus is favorable. Experiments show that the full field average Modulation Transfer Function(MTF) of each focus at the Nyquist frequency is over than 0.524, which meets the system requirements.