A preparation of a homogeneous polysaccharide from a Radix Puerariae aqueous extract is provided and the lipid-lowering activity of the polysaccharide is studied. It is proved through in vivo experiments that the homogeneous polysaccharide QL extracted from Radix Puerariae (a genuine medicinal material in Jiangxi Province) in the present disclosure has significant lipid-lowering activity, can significantly reduce a serum triglyceride content and a liver index, and can be used to develop a potential safe and effective lipid-lowering drug.