The scaling effect of rockfill affects the accuracy of its mechanical parameters. A large triaxial shear test of φ500×1000mm (maximum particle size of 100mm) and φ300×700mm (maximum particle size of 60mm) was carried out on a rockfill, and the test process was simulated by PFC3D to further explore the influence of scale on the stress-strain Poisson ratio and elastic modulus of rockfill. The results show that the cohesive force of the large triaxial test is smaller than that of the large triaxial test, and the internal friction angle is larger than that of the large triaxial test. Under the same confining pressure, large triaxial specimens reach the peak stress of failure first, and the peak stress is higher than that of super large triaxial specimens.The numerical test can reproduce the shear process of triaxial test well, and also provide a simple method for the experimental study of the scale effect of rockfill.