The electronic structure of strontium ferrite Sr3Fe 2O6 was calculated using the tight-binding linear muffin-tin orbital method (TB LMTO) in the local spin density approximation of density functional theory with Coulomb correlations correction (LSDA+U). The semiconducting character of the spectrum with charge transfer energy gap of 1.82eV was obtained in reasonably good agreement with experimental data. The iron ions are found to be in the high spin state. The calculated value of the local spin magnetic moment of Fe3+ ion is 3.94μB which is not typical for trivalent iron ion in the high spin state. It is shown that the strong hybridization between Fe3d and O2p orbitals favors the d6 L configuration of Fe3+ ion, where L is a hole in the oxygen p shell. The mechanism of oxygen transport in ferrite is discussed basing on the total energy calculations of the different spatial configurations of oxygen vacancies.