The solubility of styrene from polystyrene in supercritical carbon dioxide is measured at 323 K, 333 K, and 343K in the pressure range from 12 to 28 MPa. Based on the association concept and the theory of dense gas sorption in polymers, a displacement and association mechanism on supercritical fluid extraction of the monomer from the polymer is proposed. And, a novel mathematical model for correlating the solubility data obtained from the experiments is also proposed in the paper.