Abstract: Compared with the infrared fixed focal length lens and infrared dual-zoom lens, infrared zoom lens which has continuous variational field of view can track targets sequentially, so it is a research direction in infrared imaging technology. With the development of optical process, mechanism process, optical film coating, it is needed for infrared zoom lens not only has high ratio, but also has good athermalized and imaging performance. The configuration and design method of foreign MWIR lens with high ratio including MWIR lens with 20ratio, MWIR lens with 30ratio, MWIR lens with 300ratio were presented. A set of design experience for MWIR lens with high ratio was summarized, which is useful for the application and development of chinese MWIR lens with high ratio.