Abstract: The general corrosion behavior of four candidate materials for key high-temperature components of supercritical carbon dioxide nuclear power conversion system was studied in 650 ℃/20 MPa supercritical carbon dioxide. Morphologies, microstructures and chemical compositions of oxide films were analyzed by scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction and glow discharge optical emission spectroscopy. The results show that austenitic stainless steel 310S and 316NG, iron nickel base alloy Incoloy-800H and nickel base alloy Inconel-625 have good corrosion resistance in 650 ℃/20 MPa supercritical carbon dioxide and the corrosion kinetics follows parabolic law. The increase of Cr and Ni contents can enhance the corrosion resistance of the materials and 310S, Incoloy-800H and Inconel-625 have better corrosion resistance than 316NG. 310S and 316NG have carburizing behavior in supercritical carbon dioxide. Carburizing may accelerate the corrosion of materials and affect their mechanical properties. This study evaluates the compatibility of different candidate materials in supercritical carbon dioxide, which provides the key experimental data support for the material evaluation of the critical components of the supercritical carbon dioxide nuclear power conversion system.