Optical frequency comb is a kind of broad spectrum coherent light source, which is composed of a series of discrete spectral lines with equal frequency interval and has ultrahigh time-frequency accuracy. Since its birth, optical frequency comb has brought revolutionary changes to the development of precision spectroscopy, optical measurement, coherent optical communication, optical clock and other applications. In recent years, researchers have extended the frequency comb to the mid-infrared spectrum region (2-20 μm) by using novel laser gain media, nonlinear frequency conversion and micro-resonator techniques, and further expand the application range of optical frequency comb. In this paper, the generation mechanism, latest development and application of mid-infrared frequency comb are introduced.