The geometric and electronic properties of SrCoO2.5 have been studied using the local-spin density approximation together with the Hubbard method. The geometric optimization shows that the energy of a unit supercell for SrCoO2.5 with the space group Prima is at least 1.37 eV lower than the others, so we infer that the Pnma structure is the ground state of SrCoO2.5 at low temperature. The electronic band structure calculations demonstrate that the paramagnetic ordering SrCoO2.5 at high temperature has the character of an indirect band gap semi-conductor, while the antiferromagnetic ordering SrCoO2.5 at low temperature has the character of a conductor. The magnetism calculation shows that the magnetic moment of Co is 2.96μB, comparable with the experimental measurement at the liquid nitrogen temperature, i.e. 3.30±0.5μB.