The problem of China’s atmospheric environmental pollution is grim. Emission source of SO2 and NOx comes from thermal power plants, coal-fired boilers which are based on coal burning. The current standard of coal-fired flue gas emission is strictly defined, so that more stringent requirements of on-line monitoring technology for continuous emission of flue gas are put forward. Based on the method of differential absorption spectroscopy, the analyzer of SO2 and NO pollution gases in coal-fired power plant was studied. According to the absorption spectrum of SO2 and NO, using SiC lamp as the light source, the measurement band of 1900～2600 nm is carried out. By using the least square method, correlation coefficient of two sets of equipment is calculated. As a result, the analyzer can meet the demand of ultra low emission gas monitoring.