An experimental investigation has been conducted to reduce NOx from combustion due gases by means of corona discharge activated methane radical injection methods. Two types of corona radical injectors, the hollow needle type and the multihole type, are used in the present investigations. Experiments are conducted for the simulated flue gas (N-2: O-2:CO2 NO = 83.996:8:8:0.004) dow rate from 1 to 20 L/min., the activation voltage from 0 to 40 KV and the Ar-methane mixture gas (95:5) dow rate from 0 to 200 mL/min. The results show that the NOx reduction increases with increasing activation voltage and nonmonotonically depends on methane stoichiometry. Trace amounts of N2O and NH3 were observed as a by product.