TiO2 thin films were prepared by a magnetron sputtering technique and then annealed at different temperatures. The crystal quality, surface morphology, optical absorption and photocatalytic performance of the as deposited and annealed films were characterized and compared by XRD, AFM and ultraviolet-visible spectrometer. The results show that with the increase of annealing temperature, the TiO2 phase turns from anatase to rutile, while at 600 oC, two kinds of phase coexist. During the annealing process, the grain sizes of the TiO2 films change simutaneously. Compared with rutile, anatase phase presents better photocatalytic performance.