Abstract: Pure and Gd³⁺-doped TiO₂ nano-particle with different amounts of Gd³⁺-doping were prepared by the acid-catalyzed sol-gel method using Ti(OC₄H₉)₄ and Gd(NO₃)₃ as precursors and characterized with XRD, BET, XPS and SPS.The effects of the amount of Gd^3+-doping and calcination temperature on the photocatalytic activity for photocatalytic degradation of methylene blue (MB) in aqueous solution, phase structure, crystallite size, surface texture properties of the nanopowders were investigated,and the mechanism of the effects of Gd^3+-doping on the photocatalytic activity of TiO₂ nano-particles was also discussed in combination with the surface photoelectric properties and surface composition of the nano-particle.The results indicated that Gd³⁺-doping could enhance the photocatalytic activity of TiO₂ nano-powder as compared with pure TiO₂.0.5% (mass) Gd³⁺-doped TiO₂ nano-powder calcined at 500℃ for 2 h show the highest photocatalytic activity.The presence of Gd³⁺ in TiO₂ could inhibit the phase transformation from anatase to rutile,restrain crystal grain growth, and enhance the threshold value of photoresponse, which resulted in increase in the photoactivity.XPS result showed that Gd^3+-doping can lead to decrease in the density of surface hydroxyl groups.