First-principles calculations are employed to study the surface relaxation and electronic structure of the fully relaxed SrTiO(3) (001) oxygen-vacancy surfaces with both Sr and Ti terminations. In contrast to the perfect surface, the larger surface rumples and smaller interlayer distances have been found. Some in-gap Ti 3d states at about -1.13 eV below the Fermi level were observed in the Ti-terminated surface caused by oxygen vacancies. For the Sr-terminated oxygen-vacancy surface, some in-gap Ti 3d states move into the bulk midgap region to become partially occupied. These theoretical results are in agreement with the experimental data.