Seepage erosion in shield tunnels poses a significant threat to tunnel structure and surrounding environment. Moreover, train vibrations complicate the progress of seepage erosion. The mechanism by which vibrations affect soil particles during seepage erosion remains unclear. To investigate this, the coupled computational fluid dynamics and discrete element method (CFD-DEM) was employed to analyze the macro and micro behavior of soil particles under vibration at a fixed vibration frequency (30Hz) and varying amplitudes (i.e., 0.1 mm, 0.2 mm, 0.4 mm), focusing on cumulative mass loss, the velocity of particle and flow fields, average coordination number, and evolution of microscopic contact force. The results indicate that vibration has an aggravating effect on seepage erosion, and the effect becomes more pronounced as the amplitude increases. Vibration reduces the proportion of strong contact in C-F and forms a coarse particle skeleton structure dominated by strong contact in C-C. The coarse particle skeleton structure is adjusted to facilitate force transfer until a stable skeleton structure is formed. This research enhances the understanding of the relationship between vibration and seepage erosion.