The force constants, compliance constants and interaction coordinates are calculated from the vibrational spectral data for the two molecules, OsO₃F₂ and XeO₃F₂. The method of Isotani is applied in two different ways, one directly and another by coupling with high frequency separation technique. Other molecular constants like mean amplitudes of vibration and centrifugal distortion constants are also calculated. The values appear to be in good comparison with the literature values.