The molecular model of viscous flow of liquid proposed by Eyring is modified from two respects, namely, the activated energy of viscous flow and the frequency with which activated molecule falls into the hole. A viscosity equation with a single adjustable parameter is obtained, which can be satisfactorily used to correlate and predict the viscosity of various liquid mixtures except aqueous systems. The calculated results show that the agreement with experimental values prevails over Grunberg-Nissan and Wei-Rowley equations etc.