The work aims to study the effect of dissolved oxygen concentration on oxidation behavior of boiler metals under Oxygenation Treatment (OT) condition and the optimal dissolved oxygen concentration for OT of feedwater. The high temperature and high pressure environment in Power Plant was simulated with autoclave and SA-210C and 15CrMoG were oxidized by high temperature under different dissolved oxygen concentration. The time-weight gain curves of two materials were drawn and the oxidation kinetic equations were fitted to study the effects of OT on the kinetics. Polarization impedance(Rp) and oxide film capacitor (Qf) were obtained through electrochemical impedance spectroscopy (EIS) test and then used to analyze oxide film structure with SEM results. Reduction peak heights of Fe(II) and Fe(III) in oxide film were obtained through voltammetric scanning and then used to analyze phase composition of oxide film with XRD test. The weight gain of SA-210C and 15CrMoG after being oxidized at 50 μg/L dissolved oxygen for 30 days was 1.714 g/m2 and 1.804 g/m2, respectively. The polarization re-sistance of both materials reached the level of 106 Ω?cm2 under OT condition which was one order of magnitude higher than that of anaerobic condition and the structure of oxide film was more dense. The oxide film composition of SA-210C was Fe3O4 and that of 15CrMoG was Fe3O4+Fe2O3 under OT condition. The oxidation behavior of SA-210C and 15CrMoG at high temperature is consistent with ?m=kta law. OT significantly accelerates the growth of the initial oxide film of SA-210C, but inhibits the oxidation rate at the later stage. OT mainly affects the initial growth rate of 15CrMoG oxide film, and has few effects on the later oxidation kinetics. The optimal oxygen concentration of SA-210C and 15CrMoG is 50 μg/L.