Model tests are carried out on the jacked single piles of different diameters under model pile of different diameters in clayey soil, which aims to investigate the penetration mechanical mechanism. The results show that pile driving pressure of test pile appears linear increase basically, which is the larger when the pile diameter is larger. The load transfer performance of test piles will be affected by different diameters, and the axial force transfer capability of large diameter in the depth direction is better than that of small diameter due to the compacting effect is more obvious. Unit skin friction of pile increases gradually as the depth increases, which is larger due to the lateral extrusion force increases as the diameter increases. At the same depth, unit skin friction of two different diameters pile appears “friction fatigue”, which also decreases obviously as the depth increases. At the same time , the “friction fatigue” is more obvious as the pile diameter increases. In homogeneous clays, the piling resistance mainly includes the end resistance. The end resistance of test pile accounts for 59.5%和66.2% of the piling resistance when sinking pile ends. The end resistance and the shaft resistance are influenced by the pile diameter. For the confirmation of the jacked piling resistance, it is more rational to consider the actual value with the friction fatigue of clayey soil.