Removal of NOx (namely DeNOx) from simulated flue gas with direct current (d.c.) corona radical shower system was investigated. Steady streamer coronas occur when the flow rates of the fed gases are adjusted properly. The experimental results show that both the composition and the flow rate of the gas fed into the nozzles influence the V -I characteristic of corona discharge. The vapor in the flue gas restrains the discharge, reduces the discharge current, but enhances the DeNOx efficiency. Furthermore, removal of NOx from flue gas by radical injection associated with alkali solution (26% by weight of NaOH in water) scrubbing was carried out. Oxygen together with water vapor is fed into the nozzle electrode and the oxygen and water molecules are decomposed in the corona zone. It is found that NO and NO2 can be converted into HNO2 and HNO3, respectively, by radicals formed during the discharge process and the conversion efficiency of NOx in the plasma reactor is more than 60%. The overall DeNOx efficiency of the system reaches 81.7% after the flue gas was scrubbed by the NaOH solution.