The molecular thermodynamic model developed previously for fluids of chain-like molecules has been extended to correlate the solubilities of gases such as N-2, CO2, CH4 and C2H4 in molten polymers. Classical mixing rules with one adjustable binary parameter was used to adjust the interaction energy between segments of mixtures. For 21 binaries including 52 systems tested, the average relative deviation of pressure is 19.3%. The accuracy of the correlation can be notably improved by using two parameters k(ij) and l(ij) the latter was used to adjust the collision diameter between segments of mixtures. The average. relative deviation of pressure is lowered to 5.6%. For the systems of CO2-molten polymer, the model parameters of CO2 should be re-determined from the experimental solubility in one polymer, the accuracy of the correlation can be notably improved with the use of only one parameter. The comparisons among the calculated results of this work, SAFT and PR equation of state have been made.