Abstract: The four well-known activity coefficient models (Wilson, NKTL, McCann and UN1FAC),coupled with virial equation and tridiagonal matrix method, have been successfully applied to the vigorous computation of various non-ideal distillation processes. The N1DISTL program developed by authors has been tested for 33 distillation systems, with more than on hundred calculations performed. To make a parallel comparison of these activity coefficient models, 18 sets of binary vapor-liquid equilibrium data were chosen, each set was fitted to Wilson, NRTL and McCann equations respectively by using non-linear least square technique. The binary parameters so determined were used to predict the bubble point equilibrium data of 18 binary and 8 derived multicomponent systems. The predictions of four models were compared with experimental data. To illustrate the consistency of distillation calculation results using different activity coefficient models, four examples were presented. The temperature, flow rate and composition profiles calculated were compared and the cause of discrepancy in some cases were discussed.