Abstract: The bivariate correlation analysis of three sets of data including the emission concentration of oxynitride, reaction temperature, the content of oxygen, and the ammonia spray intensity were conducted on the basis of the on-line monitoring data of the flue emission of the SNCR process in a cement production plant. The results showed that the SNCR process needs to keep the temperature within the anomia removal window. The higher concentration of oxygen in the SNCR process would reduce the denitrification reaction, therefore, increasing the ammonia spraying amount is not the most effective way to improve the denitrification reaction.