Biomodification of polyester film is a new field which can improve the surface property of material whithout environmental pollution and high energy consumption. Bacillus B-F which was isolated from waste water could biodegrade terephthalic acid. It was fermented and the broth was concentrated and used for surface process of polyester film. The modification lasted for 20 days. The surface property of the original and modified polyester film were tested. Contact angle examination showed that the hydrophilicity and surface free energy of the film was increased; XPS tests revealed the content of oxygen increased; FTIR showed that a small quantity of phenolic hydroxyl group appeared on the surface of the film; an oxygenase catalysed action might react at the surface of the film according to the degradation pathway of the simulacrum terephthalic acid.