The principle of NDIR gas sensor is introduced in detail and basic characteristics of common sensor and NDIR gas sensor are compared and analyzed. IR source design,gas cell design,detector design,signal processing and self assembly multi gas detection system in regard to NDIR technique are expounded,which gives research direction for improving accuracy and sensitivity of gas detection. The development tendency of NDIR sensors towards small volume,multi function integration and meeting the complex application environment is prospected in this paper.