In order to investigate the dynamic behaviors of geogrid-reinforced pile-supported embankments under traffic loading, three-dimensional coupled mechanical and hydraulic numerical simulations are conducted using FLAC 3D. Four cases are studied including unreinforced and no-pile embankments, reinforced embankments, pile-supported embankments, and geogrid-reinforced pile-supported embankments. The behaviors of vertical displacement, horizontal displacement, pile-soil stress ratio, excess pore water pressure and acceleration under four cases are analyzed. It is found that the vertical displacement, nonuniform settlement and horizontal displacement of geogrid-reinforced pile-supported embankments are smaller than those of other cases due to soil arching effect and reinforcement effect. Pile-soil stress ratio decreases with the increase of loading number. The crest value of acceleration and the time for acceleration to be steady are also smaller than those of other cases. The dissipation velocity of excess pore is quicker than that of unreinforced embankments.