We present a theoretical study of germanium growth orientation dependence on SrTiO 3 surface structure using first-principles calculations. Contrary to much work on the SrTiO 3 surface which considers the simple TiO 2 termination, we work on the now well known 2 × 1 reconstructed surface, which is terminated with a TiO 2 double layer. 29 We study the oxygen reduction at this surface maintaining the 2 × 1 reconstruction. Analysis of its electronic structure shows that the reduction leads to a metallic surface and changes of the surface bond characteristics. Therefore, the growth routes for Ge epitaxy are studied. It is demonstrated that the reduction favors the creation of the Ge−O bonds by weakening the strength of the Ti−O bonds. It gives the possibility of Ge[001] growth direction, which is not possible on a nonreduced surface.