Gradient combustion technology divides the furnace space of the calciner into functional partitions through multi-stage control of the air inlet, feeding, and coal injection, establishing a combustion atmosphere environment of "strong lean oxygen reduction zone - weak lean oxygen reduction zone - combustion zone", thereby achieving source emission reduction of NO_X. This article develops an online gradient combustion calciner and a supporting swirl dispersion burner, which can increase the residence time of the strong reduction zone to 2.5~3.0 seconds and improve the self denitrification effect. The application of this technology in the Tengzhou Dongguo production line shows that, the self denitrification efficiency can reach over 70%, the stable control of NOX at the outlet of the calciner is below 260mg/Nm³, and the NOX emission control of the chimney gas is 30~50mg/Nm³. the dosage of ammonia water used in the clinker production is less than 2.5kg/t, achieving low-cost and ultra-low emission of NO_X in cement kiln flue gas.