Abstract: In order to design a two-stage zoom mid-wave infrared optical system for a 1280 pixel×1080 pixel cooled mid-wave infrared detector, the overall system structure was determined based on specified design requirements. Using zoom theory and the principle of secondary imaging, the theoretical parameters of the system were calculated. This study systematically investigated the process of establishing the initial system structure, with a focus on component lenses, optical power distribution among lenses, and lens selection. Through step-by-step and combined optimization, the final optical system design was completed. The results showed that the system achieved two-stage zoom of 180 mm/360 mm with an F-number of 2. The system met the requirement of 100% cold stop efficiency, maintained distortion below 0.3%, and achieved modulation transfer function values greater than 0.3 at a spatial frequency of 42 lp/mm. This study provides a practical and feasible method for the establishment and design of cooled infrared optical systems.