The objective of this investigation was to study the behavior of deep pile caps and the ultimate loadcarrying capacity. Four 1/10 scaled models of ninepile caps were cast and tested on vertical loads to failure. The destruction shapes of pile caps, the correlation between load and displacement, and the internal stresses were analyzed systematically. The results demonstrated that the failures of all the four models are resulted from punching shear; the internal flow of the forces in ninepile caps can be approximated by “strutandtie” model. Furthermore, the failure loads of these specimens were predicted by some of the present design methods and the calculated results were compared with the experimental loads. The comparative results also indicated that the “strutandtie” model is a more reasonable design method for deep pile caps design.