Abstract: The pile-net composite foundation was commonly used as a kind of ground reinforcement measures in recent years,and the pile-soil stress ratio is a very important parameter in the research of the composite foundation.Through the field measurements of the pile-soil stress ratio of the composite ground of a passenger traffic line,the law of the pile-soil stress ratio’s variation and the work mechanism of the pile-net composite foundation under embankment are obtained.The measured results show that: 1) the measured pile-soil stress ratio is much more less than that under rigid foundation,and the ratio achieves stable gradually by the pile-net-soil interaction;2)the effect of soil arch and the effect of tension membrane play extremely important role in the pile-net composite foundation;3)the geogrid can enhance pile-soil stress ratio of the compound foundation effectively.