The height of cushion has played a key role in bearing capacity of composite ground with cement-soil pile, so the selection of the cushion height has become a key factor in composite foundation design. Concentrating on the silty soil in Zhuhai, four kinds static load tests on cushion height of cement-soil piles composite foundation is carried out. Through the comparative analysis on the test data, the reasonable cushion height of cement-soil pile composite foundation is suggested, the load transfer mechanism of cement-soil pile composite foundation is obtained, and many factors should be taken into consideration in designing the cushion height. The results provide a valuable reference for the design of cement-soil piles composite foundation in the Zhujiang triangle district.