Abstract: Transition metals （Cr,Fe,Ni and Zn） doped TiO₂ nanoparticles were synthesized by sol-gel method using 2-hydroxyimidazole formate ionic liquid as microstructure control reagent.The prepared samples were calcined at 500 ℃,and then were characterized by BET,XRD and DRS,etc. The photocatalytic properties of the obtained TiO₂ were also tested with Acid Blue 92 as simulated pollutants.The results show that transition metals doped TiO₂ nanoparticles have a higher specific surface area and smaller particle size in comparison with those of pure TiO₂,and the absorption spectrum of transition metals doped TiO₂ shifts to visible light. According to the degradation of Acid Blue 92 in aqueous solution under UV irradiation,the photocatalytic activities of transition metal ions doped TiO₂ nanoparticles are enhanced significantly.