Abstract: Based on the Winkler model,the load transfer matrixes of single pile in elastic and elasto-plastic state in layered soil were presented to obtain the simplified nonlinear method for analysis of settlement and internal force of single pile.The sheltering effect between passive piles and soil was taken into account to modify the conventional interaction factor between two piles.The approximate approach with the concept of the interaction factor was employed to study the nonlinear behavior of pile groups with rigid cap and piled raft foundation.Because the nonhomogeneity of soil and nonlinear interaction between piles and soil was considered,the theoretical model agreed with the fact quite well.The calculated results was compared with those of the finite element and field tests,and the feasibility of the proposed model for the analysis of pile groups and piled raft foundation was proved.