Abstract: Composite films of chitosan,gelatin and chitosan oligosaccharide(COS) were prepared. The films 'structures were characterized by FT-IR. The effects of COS on physical,mechanical,antioxidant and antibacterial properties of the composite film were evaluated. The results showed that there were hydrogen bonding interactions among chitosan,gelatin and COS. The addition of proper content of COS increased the hydrophilicity of composite films, moreover, the tensile strength, water vapor barrier properties were improved, and the antioxidant and antibacterial properties were significantly improved( p < 0. 05). Composite film consisting of chitosan and gelatin with a weight ratio of 2 ∶3,1% glycerin,30% COS showed some good properties. The DPPH radical scavenging activity was enhanced by 7.03 times,moreover,the diameters of inhibition zone against Escherichia coli and Staphylococcus aureus were enlarged by 32% and 30% respectively.