The microscopic mechanism of optical anisotropy and spontaneous polarization in the tetragonal phase of AB0₃ perovskite type structure, in particular BaTi0₃, KNb0₃ and PbTi0₃, are discussed by using a microscopic model. For the optical anisotropy, we have taking into account of the dipole-dipole effect due to the ionic and electronic polarizations of the crystal and the spontaneous Kerr effect. The last effect is a cause of the strong local field acting on the constituent ions. For the spontaneous polarization we use only the dipole-dipole effect. In this microscopic model, only the Ti ions for BaTi0₃ and PbTi0₃ and Nb ions for KNb0₃ localized at the center of the unit cells of the lattice are assumed to have the spontaneous shift. The cubic-tetragonal phase transition in the three compounds above mentioned is also analyzed. It is found that the optical anisotropy, the spontaneous polarization and the nature of the phase transition are in good agreement with the experimental data.