Abstract: In this work, a commercial Chinese bayberry tannin (BT) was used to improve the properties of the casein-based film via the solvent casting method. The impacts of tannin loading content on solubility, opacity, tensile strength, morphology, water vapor permeability (WVP), thermal stability and antioxidant capacity were investigated. Based on the experimental results, ameliorating the solubility, tensile strength, WVP, thermal stability and antioxidant capacity of casein-based film. The transparency of resulting films decreased by increasing BT loading content. The casein-based film incorporated with 15wt% BT displayed the best modification effects, whose tensile strength increased by 70.9%, WVP decreased by 72.1% and DPPH radical scavenging activity increased by 18.2% compared with the native casein-based film. On this basis, BT is considered a promising multifunctional additive for casein-based film in the applications of active food packaging.