A visible-light-active mesoporous Cr-doped TiO 2 photocatalyst with worm-like channels was synthesized using an evaporation-induced self-assembly approach and characterized by X-ray powder diffraction, nitrogen adsorption–desorption, X-ray photoelectron spectroscopy, transmission electron microscope, and UV–vis diffuse reflectance, respectively. The effect of Cr 3+ doping concentration on the photocatalytic activity of mesoporous TiO 2 was investigated from 0.1 to 1 mol%. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 8 nm with high surface area of 117 m 2/g and a crystalline anatase pore wall doped by Cr 3+. Compared with pure mesoporous TiO 2, the Cr-doped TiO 2 extended the photoabsorption edge into the visible light region. The results of gaseous acetaldehyde photodecomposition showed that mesoporous Cr-doped TiO 2 exhibited higher photocatalytic activities than pure mesoporous TiO 2 and nonporous Cr-doped TiO 2 under visible light irradiation.