The invention discloses an oxidation sweetening and denitration method for hydroxyl radical of oxygen active particles injected in a flue duct, belonging to the technical field of gas ionization discharging, plasma chemistry and environmental engineering application. The invention is characterized in that the oxygen active particles (O<2+>, O3, O(<1>D), O(<3>P)) with the concentration of 80 to 400 mg/L are injected the flue, wherein the O<2+> reacts with the H2O in the flue gas to form the HO2<->initiator, and the oxygen active particles and the HO2<->initiator are subjected to the plasma reaction to form the.OH within the reaction time of 1 mu s to 1 ms. The.OH oxidizes and removes the SO2 and the NOx in the flue gas to generate the submicron acid mist with the reaction time of 1 to 1 s, then the charge coagulation is performed to collect the mixing acid liquid, and finally the sulfuric acid and the nitric acid are separated and purified by chemical methods, wherein the acid resource recovery rate is 50 to 98%. The invention has the effects and the advantages of solving the problems of the existing desulphurization and denitration method of the flue gas, realizing the novel recycling and dry desulphurization and denitration method without using catalysts, absorbent and reducing agents, and generating any re-contaminative by-product and any negative effect to the environment.