Undoped and Cr-doped Bi 12 TiO 20 (BTO) were prepared and used as photocatalysts for the degradation of formic acid both under visible light and UV irradiation. The effects of the Cr doping on the visible light response and the photocatalytic activity of BTO were investigated. The prepared catalysts were characterized by using XRD, XPS, UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy. The doping of Bi 12 TiO 20 with low concentration of Cr leads to noticeable increase in visible light absorption and decrease in the recombination rate of photo-generated electrons and holes. As a result, the Cr-doped BTO showed a higher photocatalytic activity for the degradation of formic acid both under visible light and UV irradiation, as compared with undoped BTO.