Heats of mixing were measured for the acetone-water system at 15, 25, 35 and 45 ℃, respectively. Interaction energies between the water and acetone molecules were calculated by the NRTL equation, and the effects of the interaction energy on heats of mixing were discussed. The excess Gibbs free energy and the excess entropy were calculated from the experimental data for the heat of mixing and isothermal vapor-liquid equilibria were predicted from the calculated values of excess Gibbs free energy. The results turned out to be in good agreement with literature values.