Electronic and structural properties of Nb-doped SrTiO3 are studied using the first principles density functional theory (DFT) calculations based on a plane-wave basis and pseudopotentials. Dopant formation energy, structure distortion, band structure as well as density of states have been obtained. Dopant formation energy results show that Nb preferentially enters the Ti site in SrTiO3, which is good agreement with experimental observations. The Fermi level of the Nb-doped SrTiO3 move into the bottom of conduction band, and the system undergoes an insulator-to-metal transition. Due to the appearance of the carrier impurity from Nb doping, there is a significant distortion on the top valence band. (C) 2007 Elsevier B.V. All rights reserved.