Rubberized epoxy asphalt trackbeds, incorporating crumb rubber (CR) particles within the cured matrix, demonstrate superior vibration damping and deformation resistance characteristics. Current research remains predominantly focused on macroscopic properties, leaving a critical knowledge gap regarding the particulate-scale mechanisms controlling their dynamic performance under high-speed rail loading. This study bridges this gap through advanced discrete element modeling,developing two-dimensional DEM representations of four sleeper-asphalt composite units with varying CR concentrations (0%, 2%, 4%, and 6%). The models demonstrate exceptional validation accuracy against finite element analyses, with track stiffness predictions within 96.7−152.4 kN/mm range (maximum deviation <2.07%). Our particle-scale investigation of 350 km/h loading cycles reveals three key phenomena: (1) CR content proportionally increases dynamic deformation (stabilizing at 0.5 mm for 6% CR after three loading cycles), while simultaneously enhancing elastic recovery and cumulative deformation resistance; (2) CRparticles redistribute contact forces (0−100 N), with 4% content as a critical threshold shifting behavior from aggregate-dominated to CR-controlled; (3) This transition optimizes stress distribution and force chain homogeneity, achieving optimal balance between flexibility and stability. The findings provide essential insights for designing high-performance rubber-modified railway trackbeds.