Nitrogen oxide is one of the main pollutants in the atmosphere, so it is very important to study the technology of nitrogen oxide emissions. In this paper, urea being used as reducing agent, the denitration effect and law of various experimental conditions on SNCR technology were studied， by changing the reaction temperature, NSR, O2 concentration and the other conditions,. Experimental results showed that the reaction temperature, NSR and O2 concentration had a great influence of urea on SNCR removal of NOX; the optimum denitration temperature of SNCR was about 925
, at the same time the maximum efficiency was 81%; the optimal temperature window of reduction was 875-1025
, within this interval efficiency over 50%; the optimal NSR was 1.5; denitration efficiency achieved the maximum value(83%) at 1100
in anaerobic conditions; in aerobic conditions, the maximum efficiency was achieved at about 925
; the optimum O2 concentration was between 1% and 4%.