Abstract: The p-y curve method is one of the most commonly used approaches in the analysis and design of piles under horizontal loadings. A p-y model is proposed within the framework of bounding surface elasto-plastic theory. In comparison with the traditional p-y curves, the model can simulate p-y relationships with different degrees of nonlinearity by choosing appropriate values for the model parameters, and can also simulate the soil-pile interaction under cyclic loadings. By adopting the incremental finite element method for beams on nonlinear foundation incorporating the proposed elasto-plastic p-y model, a finite element program is formulated. Soil-pile systems in the field or in the laboratory tests under monotonic or cyclic horizontal loadings are analyzed by use of the finite element program. By comparing the calculated and measured results, the capacity of the method and the proposed elasto-plastic p-y model in modeling the nonlinear response of the piles is demonstrated.