Abstract: Four well-known activity coefficient models (Wilson,NRTL,McCann and UNIFAC),coupled withvirial equation and tridiagonal matrix method,have been applied to the vigorous computation of variousnon-ideal distillation processes.The NIDISTL program developed by authors has been tested for 33 distil-lation systems,with more than one hundred calculations performed.18 sets of binary vapor-liquid equilibrium data were chosen for the parallel comparison of these activ-ity coefficient models,each set was fitted to Wilson,NRTL,and McCann equations respectively by us-ing nonlinear least square technique.The binary parameters so determined were used to predict the bubblepoint equilibrium data of 18 binary and 8 derived multicomponent systems.The predictions of four mod-els were compared with experimental data.Five examples were presented to illustrate the consistency of distillation calculation results using dif-ferent coefficient models.