A group-contribution equation of state (EOS) based on the hole theory has been developed to predict the phase equilibria of mixtures containing polar substances at high temperatures and pressures. The calculated systems are classified to be six water + hydrocarbon, seven n-alcohol + hydrocarbon, two water + n-alcohol systems and four water + hydrocarbon + hydrocarbon ternary systems. The groups cited are CH2, CH3, ACH, ACCH(3), CH2OH, CH3OH and H2O. The characteristic parameters of the solid-state molar volumes and external degree of freedoms required for the prediction have been determined by the critical temperatures and pressures of pure substances. The group interaction energy parameters have been determined by the data of vapor pressures and phase equilibria. The parameters determined by vapor pressure data are checked by predicting the vapor-liquid equilibria for benzene + heptane system. The calculated phase equilibria are in good agreement with the literature data. Moreover, the prediction performances have been compared with other group-contribution methods.