Critical loci of mixtures, which play an important role in retrograde condensation, supercritical fluid extraction(SFE), and supercritical fluid chromatography(SFC), can be determined by solving the critical loci equation along with an equation of state chosen for the mixture. In most of cubic equations of state, however, an appropriate mixing rule should be utilized for the parameters a and b inherent in them and it usually causes some error in predicting thermodynamics properties of fluid mixtures. Recently, several approximate and reasonably successful mixing rules have been proposed for the description of vapor-liquid equilibria since Huron and Vidal[1,2] developed the basic idea of so called EOS/G^E mixing rule. In this work, four different mixing rules(HV, MHV1, WS, and LCVM) based on the liquid solution models(NRTL, UNIQUAC, and UNIFAC) as well as the classical mixing rule were used to compare the results on critical loci for several binary mixtures when the SRK and PR equations of state were selected for an equation of state. The overall results on critical loci by different mixing rules used were compared and it was also shown that the WS mixing rule produced slightly better results than others even though any equation of state with particular mixing rule did not give the best results of all.