A model for correlating the phase equilibria of solid-supercritical fluid (SCF) systems has been developed. The model is based on the fact that the free solute molecules, the solvent molecules, and the solute-solvent clusters in such a solid-SCF system are in chemical equilibrium. The local density of the solvent surrounding a solute is used as one of the parameters in the model. The validity of the model is verified by correlation of the phase equilibrium data of supercritical CO2-solid systems reported in the literature. Using the solubility data, the model can be used to estimate the local density and the average number of the solvent molecules in the clusters.