Abstract: The study of the relationship of vapor liquid equilibria in the acryloni-trile-acetonitrile-water ternary system is based on a large number of experimental data. The multiparameter Wilson equation is used to correlate the vapor-liquid equilibrium data.The parameters in above equation are wholly provided from corresponding binary systems. The total average absolute arithmatic deviation of 99 data points is only 0.0098 mol fraction. It must be pointed out that this result is considerable successful in such non-ideal and partially miscible ternary system. The conjugate points of liquid-liquid equilibria can be correlated by using the same relationship, and quite good results can also be obtained. On the basis of this relationship, we plot a series of curves, such as the curves of vapor-liquid equilibrium compositions, the curves of normal boiling point of solutions, the relative volatilities of acrylonitrile to acetonitrile at different contents of water. These curves can be used easily and efficiently in design calculations.