With the development of infrared technology, the effect of infrared optical system should not be overlooked. The structural features of modern infrared optical system (such as off-axis three-mirror system, binary optical system and adaptive optical system) were analyzed on the basis of the summarizing traditional infrared optical system (such as reflective IR optical system, refractive IR optical system and catadioptric IR optical system). The advantages and disadvantages of traditional infrared optical systems and modern infrared optical systems were compared from the technical aspect, and the development tendency of the infrared optical system was explored. There is some theoretical guidance role and significance in further research and development of new infrared optical system.