Abstract: Large-scale triaxial tests were employed to investigate mechanical properties of railway ballast under different confining pressures. Meanwhile, the discrete element method (DEM) was applied to investigate the micro-characteristics of the ballast triaxial tests, in which the ballast particles were considered irregular non-breakable particles. The servo system was incorporated in the triaxial tests DEM simulation, and the relationships between the deviator stress, volume strain, confining pressure and the axial strain were analyzed. The DEM simulation results agreed well with the triaxial tests which validated the feasibility and reliability of DEM. Meanwhile, both the test and simulation results showed a strong influence of the confining pressure on the deformation and the maximum value and ratio of deviator stressby. The increase in the confining pressure leads to a decrease in ballast deformation. This information can be used in ballasted track design and maintenance.