- Thin superconducting films attract great attention as a promising material for plenty of applications. The surface determines most of the physical properties of these films. We studied the polarization effect for the  surface of perovskite ABO3 superconducting crystals on the example of SrTiO3. Optimization of the ion positions in several surface layers is provided. These ions are placed in the external field of the rest crystal. The interaction between ions is described by means of the shell model technique. We show that Ti+4, Sr2+ and O-2 ions displace differently from their crystalline sites, which leads to the creation of a dipole moment in the near-surface region.