A novel synthesis method of Glyco-drug radiotracer precursor is revealed. After completing synthesis of Z-Gly-ah (main structure), galactosamine GalNAc(OAc)4 is added to have coupling reaction. Then a product is separated directly from dichloromethane. Thus loss of galactosamine during extraction with liquid chromatography is reduced. Moreover, instead of trifluoroacetyl group, carbobenzoxy (abbreviated as Cbz or Z) is used as a protecting group to ensure uniformity of the phase. The cost and synthesis time are also dramatically reduced.