Anatase phase TiO2 thin films were prepared on microscope glass slides by r.f. magnetron sputtering using Ar and O2 mixed gases. Then tantalum modified TiO2 thin film was obtained to improve its photocatalytic activity. The films were characterized by X-ray diffraction (XRD), atomic force microscope (AFM) and UV-VIS spectrophotometer. The results indicated that using of proper quantity of Ta to modify the surface of TiO2 thin film can improve its photocatalytic activity.