The crystal lattice and the bond valence structure of perovskite system La1−xSrxCoO3 are reported. The atomic valences for the given perovskites were determined on the basis of bond-valence theory. For the studied compounds the failure of distortion theorem was observed, and the non-stoichiometry of oxygen was estimated. The model for oxygen distribution is then suggested. The relationship between the grain diameter and oxygen content is discussed.