Five preparation methods were used to purify the crude polysaccharide whichwas the co-products of preparation saponin from Ophiopogonis japonicus ( Thunb. ) Ker-Gawl. The results indicate that the method of enzyme hydrolysis could purify the crude polysaccharide efficiently. The content of polysaccharide is more than 85% and could be used as the foods and medicine raw material. Advanced test showed that the polysaccharide is mainly consist of glucose, fructose, xylose, rhamnose and galactose.