Phase equilibria were experimentally investigated at 1173 and 1523 K at the BaO-rich region in the BaO–SiO2 system. The phase assemblages were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive X-ray analysis. Substitutional solution model and associate model were employed to describe the liquid phase. Two sets of self-consistent thermodynamic parameters were derived based on the obtained experimental results and literature data. Phase diagrams and thermodynamic properties were calculated using the thermodynamic parameters acquired. All the calculated results were compared with the experimental data in the present work and literature. Some new experimental studies of the melting behavior of the phase Ba3SiO5 and liquidus at the SiO2-rich corner are recommended to get a better fit for this system.