Chalcogenide glasses are excellent achromatic and athermalized infrared materials. They are the ideal candidate for key optical components in infrared optical systems. In this paper, chalcogenide glasses were used to achieve athermalization of the medium-wave infrared optical system. Firstly, the effect of temperature variation on infrared optical systems was introduced. Secondly, some aspects of properties for common chalcogenide glasses were analyzed and the advantages of chalcogenide glasses were summarized. Finally, an athermal medium-wave infrared optical system working in the manner of secondary imaging was designed. The most common aluminum alloy material was used as house material. Design results show that the image quality of the optical system is excellent in the temperature range of 0-100 ℃. High-performance medium-wave infrared optical systems can be achieved by using chalcogenide glasses with a low-cost.