Abstract: The graphic methods for calculating \rm\bar G_2 and \rm\bar G_ from the known \rm\bar G_1 (\rm\bar Gi is the partial molar property of ith component) are systematically discussed with emphasis on the indirect methods following the way \rm\bar G_1 \to \rm\bar G or \rmR(R=\frac\rmG1-\rmx_1\rm) \to \rm\bar G_2 and \rm\bar G_3. An new and simple way of de-riving Darken's and Chou's equations based on the efficient uses of fun damental thermodynamic relationships is proposed, which shosvs clearly the close links between two methods, the significances of introducing R and y (y=x₃/(x₂ +x₃)) in Chou's equations, and the main points of the indirect methods.It is theoretically concluded that Chou's method developed from and perfected Darken's method and is a good method for graphic calculations of thermodynamic properties of ternary systems. Moreover, this paper presents two criteria for verifying respectively the reliability of experimental data and calculated results in ternary systems from the known data in the related binary systems.