In recent years, with the gradual improvement of environmental awareness and the implementation of the new version of Environmental Protection Law in China, the pollutant emission indicators for petrochemical enterprises have become increasingly stricter. In order to reduce the content of nitrogen oxides (NO_x) in cracking furnace flue gas, domestic ethylene plants currently use low nitrogen burner technology to control the amount of NO_x in the flue gas. As the environmental protection requirements become more stringent, it is necessary to meet the lower NO_x emission target of cracking furnace flue gas. This paper briefly introduces the application of SCR denitration technology in the cracking furnace of a newly-built ethylene plant, specifically describes the SCR technology in the operation of cracking furnace, and puts forward some suggestions for optimization and improvement.