The two compounds of methyl p-hydroxybenzoate and propyl p-hydroxybenzoate were added into LDPE to make antibacterial masterbatch. The masterbatch were prepared for different formula antimicrobial films using of extrusion casting methods, and then the antibacterial and mildew resistance properties, as well as the mechanical and barrier properties of the films were studied. Methyl p-hydroxybenzoate and propyl p-hydroxybenzoate were found showing synergistic antibacterial effect. When the ratio was 23, the antibacterial rate reached 99.67% (E.coli) and 99.59% (Staphylococcus aureus) respectively, and the mold mildew grade reached Level 1, with a strong anti-bacterial and anti-mildew effect. The addition of p-hydroxybenzoate had little effect on the mechanical properties, which was slightly better than that of LDPE at the ratio of 23, and the water permeability decreased by 34.73%, with the air permeability decreased by 5.32% and barrier performance improved. When the ratio of the two was 23, the antibacterial and mouldproof LDPE film had the best application effect, and it was expected to be used in the inner layer of low water activity food package.