Experiment on NOx reduction by advanced reburning in cement precalciner was performed on a laboratory-scale circulating fluidized bed reactor. In reburning zone, the order of the adsorption ability on CaO surface is CO2 > NO > CO, CO2 occupies a large fraction of the active sites to inhibits NO reduction by CO, the decrement of NO reduction rate is about 35% when CO2 increases from 15% to 30%, and the increment of NO reduction rate is about 40% when temperature increases from 850 degrees C to 1050 degrees C. In SNCR zone, CO2 concentration has an optimal range (25-27%) due to the competitive adsorption of CO2 and NH3 and the formation of (NH2)(2)CO on CaO surface, the optimal temperature range becomes narrow (850-975 degrees C) in comparison with that in utility boiler, the optimal concentration of O-2 is in the range of 2% to 3.3%, and NO reduction rate reaches above 75% at 900-970 degrees C.