Abstract: In view of the scale effects of deformation characteristics of rockfill, based on the contact deformation theory, the research is carried out from the perspective of particle sizes, specimen sizes and external factors, combined with the test method. The exponential correlation model between the particle sizes and the normalized compression modulus is established. The deformation reliability of compression tests is demonstrated when the particle size ratio is greater than 5. The influence rules and internal mechanism of five external factors on the scale effects, namely, the lateral limit condition, the dry density, the edge breakage and the load level, are revealed, and the relevant models for each factor and deformation are established respectively. Based on the field experiments, a multi-scale unified correction model is established, which takes into account the crushed material (rockfill) and the non-crushed materials (gravel). The applicability and reliability of the multi-scale unified correction model for deformation calculation are verified by modifying the parameters and deformation calculation of the EB model for dam rockfill. The accuracy of the model is about 20% higher than that of the direct scale tests. This provides a new thinking method and solution path to solve the inaccuracy of dam deformation prediction.