Abstract: A new geometric asymmetric model for predicting t thermodynamic properties of ternary system from three sub-binaries is presented. Its analytical expression with good calculating accuracy is most simple in present asymmetric models. The new model was applied to predict the enthalpies of mixing of the Bi-Ga-Sn, Au-Ag-Sn and NaCl-KCl-CaCl₂ ternary systems which were in good agreements with experimental data. At present work, based on thermodynamic principles, the importance of the choice of symmetric component is also discussed.