Objective This study aims to develop a green safe and low-cost food fresh-keeping film with well-defined functional properties and controllable quality. Methods Using chitosan as the film-forming matrix and gallic acid an antioxidant monomer as the functional component five chitosan CS -based films were prepared by incorporating gallic acid at different mass concentrations 0% 0. 05% 0. 1% 0. 2% and 0. 4% w / v respectively . The effects of different concentrations of gallic acid on the physicochemical properties mechanical performance and antioxidant activity of composite films were systematically investigated. The structure of the composite film was characterized by Fourier transform infrared spectroscopy FTIR X-ray diffraction XRD and scanning electron microscopy SEM . The preservation efficacy of the composite films on freshly prepared sesame oil was evaluated using an oven accelerated oxidation test. Results The addition of gallic acid caused the overall color of the composite film to be reddish or yellowish. It reduced the thickness water content water vapor permeability coefficient and elongation at break of the film and increased tensile strength opacity and water solubility. Furthermore the incorporation of gallic acid altered the crystalline morphology of chitosan endowed the films with potent free radical scavenging capacity against both DPPH and ABTS radicals and effectively delayed the oxidation and rancidity of sesame oil. Conclusion CS-based films incorporated with gallic acid can be used to prepare a good fresh-keeping film with good antioxidant activity environmental friendliness safety and low cost. The GA-2 composite film with a gallic acid mass concentration of 0. 1% exhibits the best overall performance.