Although there are many publications about S-doped TiO2, the related mechanism is still not well elucidated. In order to investigate the origin and trend of S substituting for O in TiO2 crystal lattice with proper dopant concentration, a combination of DFT calculation and experiment was used. Bader charge and electronic location function analysis indicate that the largely ionic character between Ti and S bonding in titanium dioxide decreases and there is free electron gas like behavior around S and neighbor Ti for the S-doped anatase TiO2. From DFT calculation, ST2.78 model is found to stabilize the structure of S substitution for lattice O with lower formation energy and its absorbance in visible light increases. Experiment results demonstrate that the sulfur doping results in the shift of the absorption edge for TiO2 to lower energy region, which leads to the nanoparticles active within the wavelength range of 650 nm. (C) 2014 Elsevier B. V. All rights reserved.