The DDLC mixing rule has been developed for MH equation of state on the basis of two-fluid theory and the local mole fraction expression of a generalized NRTL model. It can be used to correlate the properties of most fluids under high pressure. The critical loci of 7 binary hydrocarbon mixtures and 17 typical binary systems

including polar-polar and nonpolar-polar system

are calculated by using the new mixing rule and the criteria for the critical point of a mixture suggested by Heidemann and Khalil. The accuracy is better than or comparable to commonly used cubic equation of state

and the improvement of evaluating Vc is most remarkable.