Field of View (FOV) is one of the important parameters of an infrared optical system. It is inversely proportional to the focal length of the optical system. The FOV can be adjusted by changing the focal length or by zooming. The core of this adjustment is the zoom lens. The FOV concept of an infrared optical system is analyzed in detail. The idea and development trend of infrared zoom technology are presented mainly on the basis of the related papers published domestically.