Abstract: Abuse of antibiotics has become a worldwide problem, and looking for green antibiotics with high safety, less side effects and low drug resistance is of great significance to human development.In present work, commercial xanthan gum was degraded by an endophytic fungus Chaetomium globosum CGMCC 6882.Then the culture broth was processed by filtering sterilization, gradient ethanol percipitation, deproteinization, decoloration seperation by column chromatography and freeze-drying to obtain, one xanthan oligosaccharide with molecular weight of 4.070×10⁴ Da.Antibacterial results demonstrated that Escherichia coli and Staphylococcus aureus were highly sensitive to a certain concentration of xanthan oligosaccharide.Minimum inhibition concentration(MIC)and minimum bactericidal concentration(MBC)of xanthan oligosaccharide on E.coli were 2.50 mg/mL and 10.00 mg/mL, and which on S.aureus were 0.63 mg/mL and 1.25 mg/mL, respectively.Furthermore, the xanthan oligosaccharide produced in this work by C.globosum CGMCC 6882 biodegradation could be used as a potential green antibiotic in agricultural, breeding, food and medicinal industries.