Researches show that the production of nitrogen oxides (NO_X) is inevitable during fuel combustion, and nitrogen oxides are the main pollutants that form acid rain and damage ozone layer, so industrial emissions of nitrogen oxides have been listed as the major pollutants to be controlled. At present, ethylene cracking furnaces mainly use low nitrogen burners to reduce the nitrogen oxide content of flue gas. However, with the further stringent environmental requirements, the nitrogen oxide content of flue gas from cracking furnace have to meet lower emission targets. This paper introduces the application of SCR denitrification technology in the cracking furnace of a new ethylene plant in China, and puts forward some suggestions for optimization and improvement.