To fully understand the synergistic effect of B/N codoping on the visible-light photocatalytic activity of anatase TiO2 with exposed {0 0 1} facet, a combination of Density Functional Theory (DFT) calculation by GGA + U method and experiment has been performed. Bader charge and Electronic Location Function (ELF) analysis reveal that there is free electron-gas like behavior around N and neighbor B for B/N-codoped anatase TiO2 with exposed {0 0 1} facet, and its visible-light absorbance increases, which may promote Ti4+ reduction to Ti3+. The results of calculation and experiment demonstrate that B/N codoping leads to the shift of the absorption edge of the TiO2 to lower energy region, and thus makes its photocatalysis active within the wavelength of 600 nm.