The phase behavior and critical parameters of (CO(2) + CH(3)CO(3)CH(3)) have been determined using a high-pressure, variable-volume view cell, and their densities have also been measured in sub- or supercritical regions The isothermal compressibility, K(T), was calculated from the density of the binary mixtures The transition points, bubble point, dew point, and critical point, have been measured with concentrations of dimethyl carbonate from mole fractions of (0.0242 to 0 1484), temperatures from (308 15 to 337 45) K, and pressures from (6 16 to 16.67) MPa. It is demonstrated that the density and KT are sensitive to the pressure as the pressure gets close to the critical point of the binary mixtures KT also increases sharply when the pressure approaches the dew points or bubble points at other compositions near the critical composition. When the pressure is much higher than the phase transition pressure or the composition is far from the critical composition. K(T) is rather small, and the effect of pressure on K(T) is fairly limited. The phase boundary data of the binary mixtures can he correlated well by the Peng-Robinson equation of state (PR EoS) with two binary parameters.