Abstract: Accurate prediction of pile foundation and superstructure responses under seismic loading relies on realistic modeling of pile-soil interaction. However, conventional approaches neglect the kinematic loads imparted to the pile and the hysteretic and weakening characteristics of the soil under cyclic loading, resulting in significant prediction errors. To address these shortcomings, a simple and engineering-applicable fitting p-y curve model is proposed based on the total-displacement-loading extended mobilized strength design method (T-EMSD). The evolution of soil undrained shear strength with cyclic plastic accumulation strain is integrated into the model, and, by invoking boundary-interface theory, a cyclic p-y curve accounting for soil weakening is constructed. A time-domain nonlinear seismic response analysis method for piles foundation is developed within the beam-on-nonlinear Winkler foundation (BNWF) framework. Through centrifuge tests and numerical simulations of actual engineering cases, the proposed method is validated. The results indicate that, compared to conventional methods, this approach significantly reduces errors in predicting the internal forces of the pile and can more accurately simulate the seismic response of pile foundation.