Abstract: A method of preparing a hydrogel product comprising crosslinked glycosaminoglycan molecules, comprising the steps of: (a) providing a mixed solution of glycosaminoglycan molecules, a di- or multinucleophilic functional crosslinker, and a mononucleophilic functional graft chain; (b) activating carboxyl groups on the glycosaminoglycan molecules with a coupling agent to form activated glycosaminoglycan molecules; and (c) simultaneously crosslinking the activated glycosaminoglycan molecules and grafting the graft chain to the activated glycosaminoglycan molecules by reacting the nucleophiles with the activated carboxyl groups.