NOx analyzer adopts chemiluminescence method and combines with advanced microprocessor technology. It provides accurate and reliable detection of NOx at ppb~ppm level which meets the requirements of ambient gas monitoring and online monitoring of pollution source with dilution method. The operation principle is based on chemiluminescence method. After absorbing the chemical energy and the reacting with O3, NO is inspired to excited state and once it returns to ground state, it will release energy in form of light quantum. The intensity of light emission is directly proportional to gas concentration, which could realize quantitative measurement. This analyzer can completely control all functions and also provides online instruction for important work parameters. Real time auto compensation for temperature and pressure will be made during measurement.