The La3+/ZnO photocatalytic film catalyst was prepared by sol-gel method with zinc acetate as zinc source. The samples were characterized by XRD, SEM, XPS and UV-vis. The photocatalytic properties of thin film catalyst under UV light were investigated with sulfamethazine as the target decomposition. The results showed that lanthanum as trivalent positive ions exists in the film, and lanthanum was successfully mixed into ZnO crystal lattice; lanthanum doping reduced the gap width of the catalyst, the crystal particles decreased, and the specific surface area increased; The surface of thin film catalyst was uniform; Lanthanum doped ZnO films had a higher catalytic efficiency for antibiotics. This work will bring about potential application in treatment of antibiotic pollutant