A comprehensive investigation into the compression characteristics and particle crushing behavior of rockfill samples has revealed a significant scale effect, while the study on influences of scale method, maximum particle size, and sample dimensions have been found to be relatively less significant. To begin with, confined compression tests and screening tests were conducted to study the size effect of limestone rockfill. The study examined the variations of compression coefficient and particle crushing behavior with respect to the scale method, sample dimensions, and maximum particle size. Results indicate that compression coefficient initially decreases and then increases with the increase in coarse particle content within the sample. Moreover, a positive correlation was observed between the compression coefficient and the maximum particle size of the sample, while a negative correlation was found between compression coefficient and sample size. To assess the degree of particle breakage, a relative particle crushing rate was employed to establish a power function relationship between the scale method and the relative particle crushing rate. The patterns of particle crushing rate development in relation to sample size and maximum particle size can be fitted into a curved surface equation. The findings of this research contribute to the establishment of a constitutive model that accounts for the scale effect.