TiO2 and Sn4+-doped TiO2 were prepared by sol-gel method and characterized by the techniques such as XRD, SEM and DRS. The photocatalytic degradation of methylene blue (MB) in aqueous solution was used as a probe reaction to evaluate their photocatalytic activity. The matrix distortion of TiO2 increases after Sn4+ doping and a blue-shift of the absorption profile are clearly observed. The results show that doped Sn4+ inhibits the phase transformation of TiO2 from anatase to rutile, decreases the diameter of TiO2 and significantly enhance the photocatalytic activity of TiO2. The Sn4+-doped into TiO2 exert a synergistic effect on their photocatalytic activity.