TiO2 nanoparticles were prepared by a novel alkoxide sol precipitation in concentrated nitric acid.The structure and properties of them were characterized by XRD,TEM,TEM and Uv-vis measurements.With the photocatalytic degradation of Cationic Brilliant Red 5GN under UV irradiation in fluidized photoreator as model reaction,the photocatalytic properties of them were investigated.The results indicated that the size of nanopaticle calcined at 500℃ was 15.8 nm and the transformation from anatase to rutile happened between 500℃ and 600℃.It was found that photocatalytic reaction rate for 5GN of the sample prepared under the optimized condition was 2.34 times of that of commerical TiO2.