Accurate detection of gas plays an important role in modern war,aerospace,emergency rescue,etc.Non dispersive infrared(NDIR) sensors are a kind of tools for qualitative and quantitative detection of gas based on the infrared absorption at specific wavelength,which has the advantages of real time detection,wide detection range,low consumption and long lifetime.The principles,instrumental structures and related applications of NDIR sensors are reviewed in this paper,and an outlook for the future trend of NDIR sensors is provided.