The original structure of 1#to 3#berths of a hydraulic reconstruction and expansion project in Tanzania is a gravity block，and the new-build expansion part is a pier structure with 11.54 m width. We carry out the displacement monitoring of the old gravity square block of 1#and 2#berths in the PHC pile driving process and summarize the pile sinking laws. The results show that after dredging the coral reef cushion under the gravity block，the PHC pile is driven，and the displacement of the original gravity wharf structure has a greater impact，and cracks appear on the old wharf surface and nearby buildings ground. During the pile driving process，the horizontal displacement of the interface between the different structural forms of the block is the largest. With the outer convex cross-tip pile boots，the PHC pile has the strongest penetration performance，the original horizontal displacement of the square structure of the dock is minimum，and the dock is more stable.