Abstract: In a pile-soil composite foundation with cushion,the pile would penetrate into the cushion during loading,and a negative friction resistance usually existed along the lateral interface of upper part of the pile.Based on the feature of relative slipping and mutual reaction between pile and soil that frequently occured in composite foundations,the elasto-plastic analysis method was improved by absorbing the Boussinesqs and Mindlins solutions.More-over the nonlinear characteristics of the interface between pile and soil were simulated by use of with the double fold lines model and the double curves model,respectively.The settlement of the pile-soil composite foundations was calculated by creating and solving the matrix equations regarding the node displacements of the pile and soil as unknown quantities,at the same time,the complicated distribution of stress and strain could be obtained.By comparing the calculated results of this paper with the results of the indoor model tests and the practical engineering project,the proposed method was proved to be reliable.