Experimental cloud point and bubble point data of ternary mixtures for poly(vinylacetate) (PVAc) and cosolvents in carbon dioxide (CO2) are studied using the supercritical CO2 phase behavior device. The cloud point and bubble point pressures are determined by measuring the resistance variation of photoresistance. Acetate acid and ethyl acetate have been selected as the cosolvents. These systems show phase behavior over a temperature range of 308.2-338.2 K and pressure of up to 50 MPa. The transition point pressure increases as the temperature increases. The transition point isopleths for the PVAc + CO2 + cosolvent tertiary systems show upper critical solution pressure types. The cloud point and bubble point curves for the PVAc + CO2 cosolvent systems decrease rapidly as the cosolvent concentration increases. When the mass ratio of PVAc and cosolvents is fixed at 1:7, the transition point pressures increase as CO2 increases. Compared with acetic acid and ethyl acetate, the transition point pressures of the PVAc + CO2 mixtures, containing the two cosolvents, show that the pressure for acetate acid is less than that of ethyl acetate under the same conditions. The phase behaviors of these ternary systems are calculated using the perturbed-chain statistical associating fluid theory equation of state by adjusting the binary 'interaction parameter k(ij) Our models are in very good agreement with the experimental data.