The stability, electronic structure and photocatalytic properties of the Sc-doped Sr2TiO4 are investigated by first-principles calculations based on the density functional theory. The calculated results reveal that due to the electronic changes from doping, the stability of Sr2Sc0.125Ti0.875O4 is weakened after Sc doping. Meanwhile, because the increase value of lattice parameter a is larger than that of lattice parameter c, the value of c/a decreases to 3.209 and is smaller than that of undoped Sr2TiO4. The band gap of Sr2Sc0.125Ti0.875O4 has a narrowing about 0.25 eV compared with that of undoped Sr2TiO4, resulting in the red-shift of absorption spectra edge. Particularly, the dispersion of the conduction bands and valence bands of Sr2Sc0.125Ti0.875O4 is enhanced after doping, which is preferable for the photocatalytic performance. In addition, a new weak absorption appears in the visible light region, which would somehow contribute to the photocatalytic activity of Sr2Sc0.125Ti0.875O4. (C) 2013 Elsevier B.V. All rights reserved.