Abstract: In this paper, using Lagrangian analysis method, the composite foundation with piles has been analyzed as three elements apart:the pile, the soil and their interface. And then,the distribution laws of the stresses in inhomogeneous strata and the mechanism of the three elements impacting on and responding each other have been researched. The result shows that the distribution laws of the stresses are controlled by many factors, such as the scale of the caps, the space and the elastic modulus of the piles, the nature of the soil and so on.