Abstract:Galactooligosaccharides（GOS） fingerprint can be used to provide a method for GOS commercial pro－ duction technology research， and quality control of GOS production. And it also can provide support for the re－ search of GOS degree. Ion chromatography was be used to study the separation degree and sensitivity of the GOS， then determined the method of constructing GOS fingerprint and mapping commercial GOS fingerprint. By comparison， the separation and sensitivity of ion chromatography were very suitable for mapping the finger－ prints of GOS. With ion chromatography， the fingerprint of commercial GOS were drew， and determined the dextrin fingerprint region of GOS. Then the degree of polymerization of GOS was determined preliminarily. Through mapping the fingerprints of GOS， more than 15 kinds of GOS were identified from commercial GOS raw material contains， and there were significant differences between different companies production of GOS.