Abstract: The relative between stress ratio of pile-soil and the thickness of cushion is researched by experimental and theoretical analyses. 7 experiments were conducted, including tests on 3 piles and single-pile composite-foundations. The distribution of stress and deformation in the composite-foundation were measured. The thickness of the cushion for test of 3 piles was 20cm and the test loading was 2 times of the designed one. When loading toe the designed load the pressure between the piles was 230kPa which is 160kPa higher than the bearing capacity of the original soil. The stress ratio of pilesoil was 14. 3, much less than the assumed stress ratio.When the thickness of cushion was suitable, the stress ratio is near to the assumed ratio. According to these measurements, when the thickness of cushion was 5cm, the deformation was less than the one of 20cm.Which was favorable for controlling settlement.