Abstract: The scale effect of rockfill materials is crucial to predicting the strength and deformation of earth-rockfill dams. Due to their large particle size and the experimental restrictions, large triaxial tests on full scale samples are seldom conducted. The size effect coefficient for single particle ranging from 10 to 40 mm in diameter is measured by single particle crushing tests. The discrete element method is adopted here, and the results show that this method can reproduce the strength and deformation of dam rockfill materials with scaled gradation well. The grain size distribution of the prototype samples is parallel to the scaled one, and the large samples are simulated. The strength parameters of samples with different sizes are studied. This work may offer a possible way to get the strength and deformation parameters for prototype samples from the laboratory results.