Abstract: The researches on constitutive relationship for rockfills are significant because of its wide application. Based on the theory of thermodynamics, a four-parameter K-G model is derived from the Gibbs free energy function. The model is theoretically rigorous and can reflect the nonlinearity, pressure rigidity, partly anisotropy and other engineering properties. Most importantly, only four parameters which are independent of each other are needed in this model. The iso-stress ratio tests and numerical simulations of two-dimensional CFRD validate the reasonability of the model. Furthermore, three-dimensional static calculation of Shuibuya CFRD is performed. The results show that the vertical displacement is 2.02 m, which is closer to the measured value than that of other nonlinear models. Therefore, the four-parameter K-G model can be used to calculate the stress and deformation of CFRDs.