Abstract: The corrosion behavior of P92 steel was investigated in supercritical water at 550 and 600 ℃ with SEM, EDS and XRD as to analysis the oxide morphology, structure and element distribution. The results show that oxidation of P92 steel approximately follows cubic growth kinetics in supercritical water, and the weight gain as well as oxide scale depth at 600 ℃are both as three times as than those at 550 ℃. A dual-layer structure was identified in the oxide scale. The outer layer is rich in Fe, while the inner layer is rich in Cr. The cracking and spalling of oxide film on P92 steel at 600 ℃is mainly ascribed to the largerthermal stress formed during cooling as a result of a mismatch between the thermal expansion coefficients of the metal substrate and oxide scale.