According to the mechanical characteristics of pile-net composite foundation of high fill section of soft soil subgrade under embankment load, this paper made an in-depth analysis of the load transfer mechanism from the top to the bottom. Firstly, embankment soil was simplified as an inside and outside column. Then, according to integral differential balance between the inside and the outside soil column, the height of the initial plane of equal settlement can be derived and the soil arch effect of high embankment fill can be reasonably simulated. Secondly, when the load transfers to the geotechnical cushion layer, thin film is used to simulate the load distribution between the pile and the soil. Based on the results of previous derivations, pile-net composite foundation can be divided into geogrid, pile and soil elements between the pile bodies. The pile and the soil between the piles were simplified as an elastic support. The pile-soil stress ratio calculation formula of the high fill section pile-net composite foundation can be derived. Finally, this paper studied the main influence parameters of the pile-net composite foundation pile-soil stress ratio in the high fill section. The results show that, with the increase of embankment height, the pile-soil stress ratio decreases, namely, with the increase of fill height pile and soil, the load distribution tends to be more uniform, but the increase of pile spacing or the compression modulus will increase the pile-soil stress ratio. Furthermore, the increase of geogrid tensile strength will cause the increase of pile-soil stress ratio, but the influence of geogrid tensile strength is small.