Abstract: In order to meet the application requirements of high resolution and large detection range in thermal imaging field, based on the theory of mechanical positive compensation zoom, an objective lens with the long focal length was used as the prototype and a floating diaphragm structure was adopted, and a long-wave infrared imaging system with high-resolution and high-rate was designed. The primary parameters of this system include F-number of 1.2, zoom ratio of 40^×, focal length ranging from 5.86 mm to 234.76 mm, and athermalization temperature ranging from −40 ℃ to 60 ℃, which is adapted to the long-wave infrared focal plane detector with the pixel size of 12 μm.