In order to determine the optimal oxygenated concentration under feedwater oxygenated treatment(OT),the calculation method of critical oxygen concentration was applied,the calculated values were discussed with actual oxygenation conditions.The critical oxygen concentration curves under different pH show that with the increase of temperature,there is similar tendency for the critical oxygen concentration curves,they are first increased and then decreased.They reach the maximum value at 150℃ and are inversely proportional to pH.The concentration of oxygen in actual power plant should be controlled at about 60µg/kg,which can inhibit flow accelerated corrosion(FAC)and prevent excessive dissolved oxygen from causing high temperature corrosion and stress corrosion on HT heating surface.