The vanadium (V)-doped mesoporous titanium dioxide (TiO(2)) nanoparticles with V/Ti ratios from 0-2 wt% were prepared using sol-gel method in the presence of triblock polymers, Pluronic F127. SEM images showed that the V-doped TiO(2) nanoparticles were porous structures. The surface areas and pore sizes were in the range 85-107 m(2)/g and 12-14 nm, respectively. From XRPD, the V-doped mesoporous TiO(2) after calcination at 500 degrees C was mainly anatase phase, and the crystallite sizes were in the range 14-16 nm. TEM images showed that vanadia was doped both on the surface and in the lattice of anatase TiO(2). A slight red-shift in wavelength absorption was observed when V/Ti ratio increased from 0 to 2 wt%. Addition of vanadium ion slightly decreased the photocatalytic activity of TiO(2) toward the decolorization of MB under the illumination of UV light at 305 nm. However, a 1.6-1.8 times increase in rate constants for MB photodegradation was observed when 0.5-1.0 wt% V-doped TiO(2) was illumined by solar simulator at AM 1.5. These results demonstrated that the doping of low concentrations of V ion into mesoporous TiO(2) enhance the photocatalytic activity of mesoporous TiO(2) towards photodecomposition of azo dye in the visible range.