In order to investigate the dynamic behavior of geogrid reinforced pile supported embankments (GRPS) under moving load, a three dimensional coupled mechanical and hydraulic model was built by FLAC 3D. The results from two cases including unreinforced and no pile embankments, and geogrid reinforced pile supported embankments were presented. The behaviors of vertical displacement, pile soil stress ratio, excess pore water pressure, and vertical acceleration under two cases were compared and discussed. Additionally, studies on the effect of speed and weight of the moving load were performed. It is indicated that the value of vertical displacement, pile soil stress ratio, excess pore water pressure, and vertical acceleration of GRPS decrease evidently compared with those of unreinforced and no pile embankment, which is caused by the soil arching effect and the reinforcement effect. It is also shown that the greater the axle load value is, the less the beneficial effect of GRPS on the vertical displacement. With the increase of the moving speed of the load, the vertical displacement increases.