Removal of NOx (DeNOx, NOx is the total of NO and NO2) from flue gas by radical injection has been investigated. The discharge characteristics were examined and the steady streamer corona was acquired by adjusting the nozzle gases properly. It was found that an increase in the voltage resulted in a decrease in the NO concentration and the concentration of the NO2 increased at low voltages but decreased as the voltage rose to a certain level. The DeNOx efficiency increased as the applied voltage rose and reached a maximum of 70% when the voltage approached the break. down voltage. The hypotheticaI mechanism Of NOx removal suggested that the radicals formed in the discharge process converted the NO and NO2 into acidic species. The Monte CarlO method was used to calculate the rate COemcients and the productivity of the radicals, and then the concentrations of both NO and NO2 and the DeNOx emciencies were calcu. lated with chemical kinetics. The calculated DeNo, efficien. cies were comparable with the experimental DeNOx efficien-cies at low voltages, but were lower at high voltages.