Emission regulation is being tightened up recently to prevent expansion of air pollution. Economic and efficient technologies are desired to process NO_x generated in combustion of fossil fuel. One of the candidate technologies to process NO_x is the denitrification of flue gas by pulsed corona discharge, which has been demonstrated experimentally to have the high deNO_x performance. However, the optimization of operation conditions and the appropriate understanding of the deNO_x process are still remained not to be cleared. Therefore, we have simulated in this study the deNO_x process added by hydrocarbon such as ethylene to give its proper operation conditions and its main reaction paths to remove NO_x, following our previous study on ammonia addition. The simulated results show that the removal efficiency in a case of ethylene addition becomes lower than that in ammonia addition, but the deNO_x energy consumption rate becomes lower than the ammonia injection case. However, the ethylene injection leads to produce the pollutant of formaldehyde, which limits the allowable amount of injected ethylene. In a case of propylene injection its deNO_x performance is better than the ethylene addition case, because propylene reacts with OH radical more than ethylene to oxide NO_x. However, formaldehyde is also produced in propylene injection case, limiting the allowable amount of injected propylene.