The basic feature of liquid molecules is non-random migration. The cells made up of the molecules are not the prison cages restraining themselves but are the carriers on which they are migrating. Based on this idea, new expressions for configurational partition function as well as the excess Gibbs energy of liquids and their mixtures have been derived from statistical thermodynamics. This has resulted in the establishment of a new thermodynamic model of liquid mixtures. The model has been verified to be quits convenient and reliable in predicting the thermodynamic properties of liquid alloys.