The invention relates to a method for preparing high-purity Gadobutrol. The method uses 3-(1,4,7,10-tetraazacyclododecane-1-yl)butane-1,2,4-triol to react with bromoacetonitrile or bromoacetamide, anobtained intermediate is hydrolyzed under an alkaline condition, and a hydrolysate is complexed with a gadolinium ion source to obtain the high-purity Gadobutrol. The preparation process of the methodis simple and mild, and the method is suitable for large-scale process production.