Abstract: Analyzed is the casing sample with early-stage failure under the Method A test of hydrogen sulfide stress corrosion.The analysis reveals that Type B aluminide strip-inclusion may lead to early-stage failure of the sample under Method A test of hydrogen sulfide stress corrosion;Type B inclusions presenting as flakes on the sample surface or inside the sample are regarded as potential crack sources;and likely, Type D spherical inclusions as crack sources may also cause sample failure under Method A test of hydrogen sulfide stress corrosion;It is regarded that one of the major approaches to enhancing the qualifcation rate of the Method A test of hydrogen sulfide stress corrosion of the SSC casing is improving the steel-making process by means of various measures for reducing inclusion quantities.