Abstract: With the country's increasingly strict requirements for the emission of air pollutants from coal-fired power plants,circulating fluidized bed boiler has attracted more and more attention because of its good adaptability to coal and low emission of air pollutants. In order to study the emission law of air pollutants in CFB and provide a scientific basis for the actual operation,and based on the combustion mechanism of CFB boiler,the coal in the boiler was divided into volatile and burning carbon. The formation of sulfur dioxide and nitrogen oxide was also divided into two parts,one was generated immediately with the combustion of volatile matter,the other was generated with the combustion of burning carbon. The amount of sulfur dioxide removal in the furnace mainly focused on the calcium sulfur ratio,while the amount of nitrogen oxide self reduction in the furnace was mainly related to the amount of burning carbon and carbon monoxide concentration in the furnace. On this basis,the models of SO2 concentration and NOxconcentration at the inlet of desulfurization tower were derived. The model has been verified on the operation data of a 330 MW subcritical circulating fluidized bed. The calculated value of the model is in good agreement with the actual value,and it is about 2-4 minutes ahead of the actual value,which eliminates the measurement delay caused by the location of the measurement points of air pollutants,and has a good prediction effect. The relationship between the amount of burning carbon in the furnace and the sulfur dioxide concentration at the inlet of the desulfurization tower and the nitrogen oxide concentration at the inlet of SNCR was studied. The calculation results show that the change trend of the amount of burning carbon is the same as that of the sulfur dioxide concentration at the inlet of the desulfurization tower and is the opposite with that of the nitrogen oxide concentration at the inlet of SNCR when the desulfurizer does not change much. At last,the model was used to calculate after changing the air volume and coal volume on the original operation data. The results show that the increase of air volume will reduce the sulfur dioxide concentration at the inlet of desulfurization tower under the condition of constant coal quantity,but increase the nitrogen oxide concentration at the inlet of SNCR. However,the effect of coal volume increase on the concentration of air pollutants emission is opposite to that of air volume increase. The calculation results have a certain guiding effect on the actual operation.