Abstract: Coarse-grained soils exhibit evident dilatancy, and they do not obey the Hook’s law. Eleven groups of triaxial tests on eight kinds of particle materials are conducted. In order to separate the observed volumetric strain, the volumetric strain is viewed as two parts induced respectively by spherical stress and deviatoric stress, and the elastic Poisson’s ratio is assumed as constant. The axial strain and volumetric strain caused by the shear stress are assumed to obey the Rowe dilatancy law. The analysis shows that the parameter Kf is in good agreement with the normalization for any particle materials, which means the parameter Kf is approximately constant. The relationship between stress state and three parameters including volumetric strain modulus Kp, dilatancy modulus Kq, shear modulus G is established on the basis of the Duncan-Chang’s model and Rowe dilatancy law. A new nonlinear dilatancy model is initially proposed, and it can be seen as an improved Duncan-Chang’s model. The proposed model can well depict the processes of volumetric strains for different particle materials, and it is a simple and practical nonlinear dilatancy model with clear physical concept.