Large diameter pile with variable cross-sections is applied to the region of bride engineering and foundation treatment. It is necessary to study the vertical bearing behaviors and working mechanism. The relation between vertical bearing capacity and settlement & distribution of the axial forces and skin friction along pile and failure mode of the pile are discussed based on laboratory test. According to the test

it is concluded that it is clear that the vertical bearing behaviors of the pile is affected by the ratio of variable diameters b value; the b is more smaller

the vertical bearing capacity is more smaller. It is proved that how to choose the b is controlled by the lateral bearing behaviors. The squeezing effect is not clear to improve the vertical bearing capacity unless the top displacement of the pile reaches a certain value.