Aim\ To investigate the calculation of the anharmonic effect in the lattice vibrations. Methods\ It is assumed that the energy of an anharmonic vibrator can be expanded in powers of the perturbation parameter \%g\%

and the coefficient can be determined in perturbation expansion.Results\ The computing formula of energy levels is given

which is described in the second order approximation. We obtain the computing methods for determining the anharmonic coefficients \%g\-3\% and \%g\-4\%. Conclusion\ The method can be applied to the perturbative approximation of interatomic potentials to a certain extent.