A method for refining sugammadex sodium is provided: adding a protective agent to crude sugammadex sodium, and obtaining pure sugammadex sodium by performing recrystallization under the protection of inert gas. Among them, the protective agent is one or a mixture of two or more, in any ratio, selected from the group consisting of mercaptoethanol, thioglycolate, thioglycolate ester, mercaptopropionate, mercaptopropionate ester, glutathione, cysteine, cystamine, dithioerythritol, dithiothreitol, trisubstituted organophosphorus compound, and salt of the trisubstituted organophosphorus compound. The method is simple in operation, high in product purity, good in economy, and more suitable for industrial production.