Abstract: Xianli Wharf of Doumen Port in Zhuhai City is founded by using vertical piles. After 13 years of operation, lot of horizontal cracks appear in the top of some piles, which seriously threatens the safety of the wharf. To make clear the cracking mechanism and develop the scheme of strengthening the piles, the geological investigation, physical model tests and numerical simulation are carried out. The research shows that the ship mooring force and the slurry dredging procedure in front of the wharf cause the horizontal displacements of the wharf platform toward the sea, resulting in large bending moments acting on the pile top. For the first row of piles near the shore, the bending moment is the largest because of the shortest free deformation section above the mud surface and the insufficient flexibility, therefore the cracks appear first in the first row of piles. After the first row of piles are cracked, the stress adjustment in the plate-pile structure may cause the second and third row piles to crack successively. Based on the above understanding, the wharf is reinforced by the mounting rebars between the embankment concrete floor and the wharf platform, which effectively prevents the platform from continuing to move outwards, and thus effectively limits the further generation of the pile cracks. In this way, the wharf restore its safe operation state.