The phase equilibria for the systems of carbon dioxide-organic substances which are quite unsym-metric mixtures at supercritical state, polar-polar mixtures and polar-nonpolar mixtures under moderate pressure are predicted by using Patel-Teja equation of state with two different mixing rules; One is the 1-fluid quadratic mixing rule by van der Waals, that is usually applied to nonpolar mixtures, and the other is the mixing rule based on Wilson’s local mole composition model. The predicted pressure and vapor composition by using the equation of state with local composition mixing rule are in better agreement with the observed data from literature, comparing with the quadratic mixing rule.