The possibility for simulation of thermodynamic parameters of MO-B ₂O₃-SiO₂ melts (M = Ca, Sr, Ba) in terms of the UNIQUAC associated solution theory was demonstrated using the experimental data obtained previously by high-temperature mass spectrometry (1650-1800 K). The calculated numbers of different bonds formed in the examined melts were found to correlate with the deviations of their thermodynamic parameters from ideality.