Four different scaling methods, including scalping method, equal-weight replacement method, similar grading method and mixing method were used to obtain the maximum dry density in laboratory according to the original average design gradation curve of rockfill in the Shuangjiangkou core-wall rockfill dam. Based on the test results and gradation equation of soil, a quantitative index of gradation composed of grading area and the content of grains smaller than 5 mm ( P 5) was adopted. The relationship of dry density versus grading area before tests, P 5 and maximum particle size was fitted. According to the relationship, the maximum dry density of the real gradation can be determined. The fitting formula between the quantified index of gradation before and after the test was obtained, and the relative change B w of the quantified index of gradation before and after the test was used as the quantitative index of particle breakage to discuss the influence of scaling method on the particle breakage of coarse particles during the compaction process. The results show that B w decreases with the increase of particle size for equal-weight replacement method, but B w increases with the increase of particle size for scalping method, similar grading method and mixing method.