Abstract: Through the comparison of the model test results and the numerical analysis, the loading transfer mechanism of pile in four-pile foundation is summarized, the back pressure characteristic of the cap and the additional pressure distribution in the soil are depicted, and the load sharing behavior of piles and soil is compared. By the analysis of the tests results, the conclusion is drawn as follows: the resist and strengthening action of piles in piles-soil-cap inte raction are proved by tests results; the pile shows a nonlinear working behavior before the soil turn into nonlinear working period. The tests results not only va lidate some aspects of the suppositions of the composite pile foundation theory, but also provide the proof for further research.