Abstract: A method for determining the purity of chitin was mainly studied.First, a given amount of chitin was hydrolyzed in 8 mol/L hydrochloride solution at 110℃ for 4 hours, and then the resulting glucosamine hydrochloride was reacted with N,O-bis(trimethylsilyl)trifluoroacetamide and 1% trimethylchlorosilane in the hydroxylamine solution of pyridine at 70℃ for 20 minutes, and its derivative was analyzed by gas chromatography with a capillary column.The gas chromatography method was also compared with a colorimetric method for determining chitin.The result indicated that the gas chromatography was more sensitive and accurate than the colorimetry.