Abstract: Un-doped,N-doped,Gd-doped and Gd-N-codoped TiO₂ nano-photocatalysts were successfully prepared by a sol-hydrothermal method. Their photocatalytic activities were evaluated by photocatalytic decoloration of methyl orange dye in aqueous solution under UV and visible light irradiation,respectively. The physicochemical properties of as-prepared samples were characterized by XRD,XPS,BET,UV-Vis and PL analytic techniques.The effect of Gd-N-codoping on the photoactivity of TiO₂ was also discussed. The results showed that Gd-doping could effectively inhibit the recombination of photogenerated electron-hole pairs,then enhancing photo quantum efficiency. Gd-doping could inhibit the growth of crystalline size and improve the surface textural properties.Therefore,the UV photoactivity was obviously enhanced by Gd-doping. N-doping could make the absorption edge red-shift to visible light range by narrowing the electronic band structure,which enhanced the visible light photoactivity. Gd-N-codoping could further increase the absorption to visible light by narrowing the electronic band structure,and further decrease the crystalline size and improve the surface textural properties,therefore increasing the thermal stability. Compared to the single-doped TiO₂,Gd-N-TiO₂ significantly improved the photoactivity for decoloring methyl orange in aqueous solution under visible light irradiation,which was ascribed to the synergetic effect of Gd-N-codoping.