This paper researches on the reduction of NOx (DeNOx) from wet flue gas by a DC corona radical shower system. The experimental results show that the water vapor in the flue gas not only reduces the corona but also reduces the discharge current. The DeNOx efficiency and the quantity of NOx removal per unit energy can be enhanced by raising the concentration of water vapor in the flue gas properly and the maximum quantity of NOx removal per unit energy is more than 25.5 g as the humidity of the flue gas ranges from 10 to 12%. The longer the flue gas resides in the reactor, the higher the DeNOx efficiency is and the lesser NOx will be reduced by per unit power.