The invention relates to a wet flue gas desulfurization and denitrification combined method. In an absorption tower, a desulfurizing agent, namely lime stone slurry reacts with SO2 in flue gas in a spraying mode, oxidizing air is input to oxidize CaSO3 in tower bottom slurry into CaSO4, and a part of tower bottom slurry is extracted and returns to the tower to be sprayed; a denitrification oxidizing agent, namely potassium permanganate, hydrogen peroxide or sodium hypochlorite and an inhibitor, namely cerium oxide or vanadium pentoxide are introduced into the original flue and introduced intothe absorption tower with the flue gas, and a denitrification reducing agent, namely urea or diammonium hydrogen phosphate and a stabilizer, namely ethylenediamine or ammonium phosphate are added into the absorption tower in the spraying mode; and the weight ratio of the denitrification oxidizing agent to the inhibitor is 1:(0.01-0.1), and the weight ratio of the denitrification reducing agent tothe stabilizer is 1:(0.0001-0.001). By the method, the problem that denitrification and desulfurization restricts each other is well solved, the flue gas is efficiently subjected to denitrification and desulfurization in the same device simultaneously to reach the discharge standard, and sulfur dioxide and nitrogen oxide are prevented from polluting an environment.