Abstract: In order to investigate the bearing capacity of steel tubular composite (STC) piles, two groups of piles, including a group of STC piles with shear ring, drilling mud skin and anticorrosion coating and a group of reinforced concrete piles, were used to conduct comparative model tests. The load-deformation curves and steel tube deformations of specimens in the two groups were compared, and the confinement effect of STC piles was analyzed by decomposition analysis method. The test and calculation results show that the bearing capacity of the STC pile was larger than that of the reinforced concrete pile significantly. Due to the confinement effect, the bearing capacity of the STC pile was increased by 9.8%even compared with the sum of the bearing capacity of a hollow steel tube and a reinforced concrete pile;at the same time, the shear strength of the core concrete was increased by 1.2 times. The confining stress of the STC pile increases with load and pile depth. The maximum confining stress of the STC pile with anticorrosion coating, drilling mud skin, and shear ring could reach 2.32 MPa. In addition, the specification ACI (2005) could apply to the ultimate bearing capacity calculation of STC piles with anticorrosion coating, drilling mud skin, and shear ring, in a way to calculate the internal strength.