Abstract: The composite foundation with concrete-cored sand-gravel pile, which is composed of the concrete-cored pile, the geosynthetic-reinforced gravel cushion and the foundation soil, is a new technology combined with the better drainage and consolidation characteristics of the sand-gravel piles, the high strength vertical capacity of the pre-cast concrete piles and the stress diffusion of the reinforced cushion, fitting for the depth mud soft soil ground with high water content. A series of field test data including surface settlement, layered settlement, lateral displacement, pile-soil stress ratio, load transfer of pile body, strength and bearing capacity under high embankment load in one project are introduced and analyzed. The research results are very important to the study on the work mechanism of the composite foundation with concrete-cored sand-gravel piles, and to the project design and construction.