Abstract: According with characteristics of interactions of vertical piles, horizontal reinforced mattress and soil, the horizontal reinforced mattress was supposed to be a thin plate, while vertical piles and soils were simplified as spring series with different rigidities respectively. A cylinder composed of a single pile and soils located in its influence area were regarded as the typical element to analyze the two-direction reinforced composite foundation. A function of the horizontal reinforced mattress deflection was deduced based on a circular thin plate on Winkler foundation, and the formula of the pile-soil stress ratio of the composite foundation was also deduced. Finally, an example was given for calculation and analysis. The main influence factors including the embankment loads, residual settlement, area replacement ratio and stiffness ratio of pile and soil are considered systemically. The change rules of pile-soil stress ratio are also investigated. The analysis result shows the good agreement with the test result.