Raman spectra of LiNbO3: MgO crystals has been obtained for the first time and compared with Raman spectra of pure LiNbO3 crystals. No change of the number, frequency, and relative intensity of Raman spectral lines of A1(TO) and E(TO) mode is found. There are only a very little increase in the line width. It is shown from this result that the more, intensive Raman spectral lines o,f A1(TO) and E(TO) vibrational mode are contributed by (NbO6) oxygen octahedra characteristic group of LiNbO3 crystals.