The finitely concentrated activity coefficients and partial molar excess properties of solvents were measured with inverse gas chromatography (IGC) in polymer solutions containing a poly(4-methylstyrene) (PMS) or a poly(vinylbenzyl chloride) (PVBC). The experimental temperature ranges were 373.15 K to 413.15 K for PMS and 353.15 K to 393.15 K for PVBC. They were over melting point or glass transition temperature of each polymer. Ten kinds of solvents (Acetone, n-Heptane, Cyclohexane, Chloroform, Methylisobutylketone, Trichlorobenzene, Benzene, Toluene, Ethylbenzene, Chlorobenzene) that are important in the chemical engineering field were arbitrarily chosen for binary polymer solutions. The external degree of freedom of original UNIFAC-FV model was empirically modified to give flexibility to itself as a C1=A+BT from the experimental data in finite concentration. The UNIFAC-FV model included a new external degree of freedom as a function of temperature. The parameters (A, B) were estimated by correlating the activities of solvent with the modified model and extended to predict the partial molar excess properties of solvents in the finite-concentrated polymer solutions. The predicted values were compared with them by original UNIFAC-FV as well as the experimental data. The results obtained with the revised model using the new parameter showed the higher quality than the results obtained by original model.