We review SAFT equation of state (EOS) which is based on TPT theory and statistical-mechanical principles, and confirm that it can be used as a useful tool to predict vapor-liquid phase equilibria of associating fluid mixtures. We examine theoretical structure of PC-SAFT EOS in great detail, and then assess the applicability and performance of the EOS while applying it to various mixtures containing nonpolar components, polar components and associating components in a stage-wise manner. In contrast to the conventional engineering EOS, PC-SAFT EOS can accurately predict nonideal behaviors of those mixtures without using semi-empirical binary interaction parameter. This is because the SAFT theory is based on a rigorous theoretical framework at molecular level which effectively accounts for various intermolecular interactions, and it thus provides substantial benefits in applying the SAFT EOS to complex thermodynamic phenomena of multi-component mixtures.