A type of polysaccharide-polypeptide hybrid material, chitin derivative with polypeptide side chains was prepared by the graft copolymerization of L-leucine N-carboxyanhydride triggered by water-soluble chitin (WSC). The studies on surface tension and aggregation demonstrated surface activity of WSC. Using this extraordinary property, the microspheres were synchronously obtained via interfacial polymerization. The method employed here to form the microspheres was in direct contrast to previous syntheses that used either templating method or oil-in-water emulsion. The study provided a facile approach for synthesizing microspheres with a variety of distinct polypeptide and regulated graft length, which had mimetic structure of glycoconjugation in extracellular matrix. Furthermore, the swelling capability of the microsphere in both acidic aqueous and organic solvents would give promising application in drug delivery.