Research of settlement and load transfer law on the composite foundation is a very important content in the composite foundation theory; then it isn’t maturity to this kind of composite foundation studying of settlement and load transfer law on theory. In this paper

based on the vertical deformation model[1] and the radial deformation model[2]

the control differential equations of pile and pile-surrounding soil are established by the elastic theory and the pile-soil displacement coordination condition. The analytical formulas calculating deformation of pile and pile-surrounding soil in the pile group composite foundation reinforcing area are derived under flexible foundation; at the same time the analytical formulas calculating the pile side shear stress and the vertical stress of pile and pile-surrounding soil are drew. For verifying feasibility of the method

the results acquired by this kind of method are contrast with the finite element method by way of calculating example. And also carrying on the model experiment. All results indicate: this kind of method has enough precision to analyzing load transfer law and deformation of the pile group composite foundation in reinforcing area under flexible foundation

it is simple to calculate

and is easy to engineering application.