In order to investigate the ability and accuracy of the UNIQUAC-based SRK EOS for prediction of high-pressure vapor-liquid equilibrium (VLE) the UNIQUAC parameter for 19 ethane binary systems have been determined. The missing binary interaction parameters are reported for PSRK, MHV1, MHV2, and LCVM mixing rules. These parameters were determined using the VLE experimental data reported in literature. The percentage average relative pressure error for 19 C2H6 binary systems is 1.93, 1.99, 2.21, and 2.03 using PSRK, MHV1, MHV2, and LCVM mixing rules, respectively. The regressed binary interaction parameters then, without any further modification, were applied to six multicomponent systems over a wide range of temperature covering more than 300 data points. The calculated percentage average relative pressure error for six multicomponent systems is 3.47, 3.75, 5.57, and 4.51 for PSRK, MHV1, MHV2, and LCVM mixing rules, respectively. Based on the results obtained in this study, it is concluded that the PSRK/UNIQUAC model has reasonable accuracy for VLE calculations and gives the most accurate results among the four mixing rules tested.