Compared with visible light imaging systems, the infrared imaging systems have the advantages of strong fogging ability, especially in the high-altitude water vapor and haze environment. and the medium-wave infrared cooling detectors have the advantage of low cost compared to long waves. Therefore, in recent years, The demand for medium-wave infrared continuous zoom systems is increasing. In this design, based on the medium-wave infrared optical system, and summarizing the advantages and disadvantages of the previous zoom structure, a zoom mechanism in the form of a cam and guide was proposed. The cam mechanism, zoom guide mechanism, and compensation guide mechanism were described in detail in this paper. The detailed analysis of the torque demand during zooming was performed. Ansys workbench was used to analyze the main components of the zoom mechanism and the stray light of the system was proposed. The adjustment results show that this kind of structure can realize medium-wave infrared continuous zooming, and the the amount of optical axis shaking during zooming is less than 0.3mrad, which meets the design requirements, and the proposed stray light suppression method effectively suppresses the system's spurious radiation and improves the lens's imaging quality; impact and vibration simulation show that the strength and stiffness of the structure meet the requirements of the mechanical environment, and the imaging system has stable performance.