This work proposes a new method for estimating the excess Gibbs energy and activity of liquid alloy based on partial pair distribution function (PPDF). This work utilized the PPDF to calculate the parameters of the MIVM, RSM, Wilson, and NRTL model. This new method offers simplicity, numerical calculation stability, and excellent reproducibility. The work examined the impact of expressing the model parameters as first-order linear functions of the components or as constants on the accuracy of the estimation. When the model parameters were treated as constants, MIVM and RSM provided an average relative deviation (ARD) of activity of less than ±20% for 15 and 10 alloys. When model parameters were expressed as a function of components, QCM showed the best estimation performance, having 9 alloys with an ARD of less than ±20%.