The invention relates to a flue gas pollutant treatment process and aims to provide a device and method for simultaneously desulfurizing and denitrifying a flue gas by ozone catalytic oxidation process. The device comprises a desulfurization and denitrification tower, an ozone generator, absorption liquid circulating equipment and desulfurization and denitrification by-product post-treatment equipment. Ozone enters from a flue or the lower part of the desulfurization and denitrification tower, a catalyst is added to an absorption liquid, and the absorption liquid is injected in from the upper part of the desulfurization and denitrification tower, so that SO2 and NO in the flue gas are oxidized by ozone with high efficiency under the action of the catalyst, and in combination with the absorption of water or alkaline substances, SO2 and NOx in the flue gas are recovered in the form of high value-added sulfuric acid and nitric acid products, or ammonium sulfate / ammonium nitrate mixed nitrogen fertilizers, potassium sulfate / potassium nitrate mixed potassium fertilizers or ammonium / potassium compound fertilizers respectively, thereby achieving resource recovery and value maximization of the desulfurization and denitrification process. The desulfurization and denitrification process provided by the invention has the advantages of simple structure, low investment and low operation cost. The desulfurization rate and the denitrification rate of the desulfurization and denitrification process provided by the invention can reach more than 96% and more than 90% respectively.