Abstract: To address the demand for high-performance infrared equipment for long-distance observation tasks such as infrared high-definition imaging and border and coastal defense, this study proposes a refracted medium-wave refrigeration zoom system. The focal-length range of the system can reach 40–900 mm, with a limited aperture of 228 mm, and the total length of the optical system is only 303 mm. Using a 15μ domestic medium-wave cooled infrared detector, the system can be applied in the temperature range of -40 ℃ to +60 ℃. Based on the optical system, a structural design was performed, and the installation and adjustment of the device were completed in a laboratory environment using equipment such as a center-deviation measuring instrument and a centering instrument. Simultaneously, the performance of the equipment was tested, and changes in the modulation transfer function in the optical system after installation and adjustment were analyzed. Test results show that the overall performance of the machine satisfies the design requirements and that the imaging quality of the outdoor target is favorable. Different focal lengths correspond to different positions at infinity.