The denitrification of YIRAN SNCR flue gas can reduce no _ x in the range of 850-1100 ℃. The main principle is that ammonia and urea are injected into the range of 850-1100 ℃ in the furnace chamber. The reductant rapidly decomposes into NH3 and reacts with nitrogen oxides in flue gas to form N2 by SNCR in the furnace. The furnace of this method is a reactor, which can be realized by retrofitting the boiler. YIRANSNCR flue gas denitrification has the characteristics of small occupation area, low investment and operation cost, simple installation and simple maintenance, which is very suitable for the flue gas denitrification work of the old power plant industrial furnace, and has high desulfurization and denitrification efficiency.