In allusion to the instability of embankment reinforced by piles when placed near the water area, a finite deference method was adopted to establish a three-dimensional numerical model to investigate the influence of water and water level on the stability. The changes of pile stress and settlement affected by water as well as water level were studied. The results revealed that the water area led to a significant increase of the pile stress which varied from the order of the formation of the water level and the embankment. The sudden decrease of water level greatly increased the risk of pile bending failure, which had an adverse impact on the stability of embankment. Without considering the influence of water area and water level change, the traditional composite foundation stability analysis method will significantly overestimate the stability of embankment.