Abstract: In order to realize the ultimate uplift capacity of model piles under excavation in sand, 19 groups of model tests are conducted on different excavation diameters, depths, and different pile lengths under the bottom of pit. The results are obtained as follows: under the same excavation depth, the larger the excavation diameter is, the lower the ultimate uplift capacity of piles is. When the excavation diameter is 30 cm(10d), the ultimate uplift capacity of piles decreases sharply. When the excavation diameter continues to increase, the decrease of the ultimate uplift capacity of pile is small, then the ultimate uplift capacity of pile tends to have a stable value. Under the same excavation depth, the shorter the pile under the bottom of pit is, the larger the loss of the ultimate uplift capacity is. The soil is overconsolidated after excavation, and the ultimate uplift capacity of piles is larger than that of the piles in the normal consolidation soil. Under the same excavation depth, the shorter the pile under the bottom of pit is, the larger the increased proportion of the ultimate uplift capacity of pile to that of the pile in the normal consolidation soil is. When the length of the pile under the bottom of the pit is the same, the deeper the excavation is, the larger the ultimate uplift capacity of pile is.