The non-dispersive infrared multi-component gas detection technology and its application in continuous emission monitoring systems (CEMS) are presented. The key factors and difficulties in multi-component gas detection are analyzed and the corresponding solutions are proposed. The composition, technical requirement and support for a non-dispersive infrared multi-component gas detection system used in CEMS are described in detail. It is concluded that it has the features of simple structure, low cost, high accuracy and good stability. The system is of some referential value to the development of multi-gas detection technology and instrument in our country.