Abstract: Field model tests and engineering application case are performed on a pile foundation under the optimal design mode of pile foundation stiffness to reduce differential settlement. Raft-soil contact pressures are measured. Based on the analysis of the measured data, the load transfer mechanism and stress ratio of pile to soil under different load levels are summarized. For the pile raft foundation, the range of load transfering to the podium at both sides of the main building is about 1.25 times the span of the podium. The intensity of spreading the load increases with the increase of the number of podium layers. Raft-soil contact pressure ratio between the edge of the raft and the center of raft is 1.89~1.23. The soil under the raft distribution load ratio is 37.5% under the working load level. The ratio increases with the increasing load level. It shows that it is reasonable that the outside of the core tube is designed as a composite pile. The bearing capacities of the piles and the cap are effectively increased. The number of the piles is reduced, and the differential settlement is minimized.