Abstract: Mechanical properties of rockfill directly affect the design, construction and operation of the rockfill dam, and have an important influence on the deformation and safety of the dam.In this study, based on the Dashixia concrete face rockfill dam project, ellipsoidal particle samples close to the real particle shape of the rockfill in 3BA zone were established by discrete element method(DEM).A series of conventional triaxial numerical tests were carried out to study the macro-microscopic mechanical properties of the rockfill in 3BA zone.The macro stress and deformation indexes of rockfill were obtained by the evolution curves of macro stress and strain under different confining pressures.The average contact force was used to divide the contact network into strong and weak subnetworks, and the coordination number distribution and topological evolution of the strong and weak contact networks were analyzed.The results showed that the secant modulus, Poisson′s ratio, peak internal friction angle change linearly with confining pressures, while the dilatancy angle changes nonlinearly with confining pressures.The topological evolution of the contact behaviors in the particle system mainly occurs in the weak contact network, which affects the macroscopic volume change of the rockfill, while the contacts in the strong contact network remains unchanged, providing a stable force transfer way for the rockfill.The research results can be used to guide the selection of macroscopic mechanical indexes under different confining pressures in practical engineering.