[en] Traditional ligand-field theory has to be improved by taking into account both pure electronic contribution and electron-phonon interaction one (including lattice-vibrational relaxation energy). By means of improved ligand-field theory, the R line, t³²₂T₁ and t³²₂T₂ lines, t²₂ (³T₁)e⁴T₂,t²₂(³T₁)e⁴T₁ and t₂e²(⁴A₂)⁴T₁ bands, g factors of t³₂⁴A₂ and t₂³² E, four strain-induced level-splittings and R-line thermal shift of MgO:V²⁺ have been calculated. The results are in very good agreement with the experimental data. It is found that for MgO:V²⁺, the contributions due to electron-phonon interaction (EPI) come from the first-order term; the contributions from the second-order and higher terms are insignificant. In thermal shift of R line of MgO:V²⁺, the temperature-dependent contribution due to EPI is dominant. The results obtained in this work may be used in theoretical calculations of other effects of EPI