Abstract: Particle crushing will change the density and gradation curves of geotechnical materials, and then influence their stress-strain behavior. The proposed gradation evolution model, based on the particle breakage characteristics of natural rocks, is to obtain the information of particle breakage and gradation which is difficult to be dealt with by normal technical means during loading process. The stress parameter of the model adopts the incremental loading method, so the model can predict the evolution of gradation during experimental process. The particle breakage characteristics and model parameters are determined through the crushing tests on a single particle. The experimental data obtained from the tests show that the particle strength obeys the Weibull distribution. In addition, the grain-size distributions after crushing tests are normally distributed, and the distributions of different groups are similar. Finally, the proposed model is proved to be able to predict the gradation variation of rockfill materials correctly through comparative analysis of the calculated results and triaxial test data.