Abstract: The general corrosion test of alloy 800H was carried out in a supercritical carbon dioxide (sCO₂) environment at 650 ℃ and 20 MPa. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to observe and analyze the morphology, composition and structure of the oxide film on the sample surface. The results showed that the corrosion weight gain of the alloy 800H in the sCO₂ was 11.2 mg/dm² after 1 000 h of corrosion. The weight gain approximately followed a parabolic growth law with time. The oxide film on the surface was mainly composed of Cr₂O₃, which was dense and protective. Carbon was deposited on the surface of the oxide film, and Al-rich and Si-rich oxides were observed at the interface between the oxide film and the matrix.