Abstract: Based on the Miedema formation heat model for binary alloy and the Toop asymmetric geometrical model, the excess free energy, formation heat, excess entropy and the interactive coefficients of activity among all components of Si-Ca-Ba ternary alloy melts were calculated thermodynamically at 1873 K. The results showed that their values are all negative, and the thermodynamic properties of the ternary alloy tend to change obviously in the zone where the Si content is high or low. The minimum values of excess free energy, formation heat and excess entropy are all found at the point where the composition shows xSi=55%, xCa=45% and xBa=0. Adding barium to Si-Ca-Ba alloy melt does not affect obviously the excess free energy, formation heat and excess entropy, and such thermodynamic properties don't change greatly with the increasing addition of barium.