To investigate the lateral response of a pile under the combined action of lateral harmonic load H（t） and vertical load V at the top of the pile， based on the Pasternak foundation and Euler beam theory， a lateral vibration analysis model of pile-soil interaction is established. The improved finite beam element method is used to solve the comprehensive stiffness matrix equation considering the P-Δ effect and soil shear effect， and the corresponding analytical solution is obtained by combining the pile-soil continuous boundary conditions. The rationality of the proposed method is verified by comparing its predictions with the results of existing analytical solutions， finite element solutions， and model tests. Finally， the main factors affecting the internal forces and deformations of the pile are analyzed. The results show that： 1） Compared with the Pasternak foundation model， the traditional Winkler foundation ignores the shear effect of the foundation soil， which exaggerates the actual force of the pile so that the calculated lateral displacement and bending moment of the pile are larger than the results obtained by the Pasternak foundation. Additionally， as the pile-soil elastic modulus ratio （Ep/Es） decreases， the difference in maximum lateral displacement and bending moment between the two foundation models becomes increasingly pronounced； 2） As the vertical load on the pile head increases， the lateral displacement and bending moment of the pile are significantly affected by the P-Δ effect. When the characteristic parameter λ of the vertical load on the pile head increases from 0 to 2， the maximum lateral displacement and bending moment of the pile increase by 40.85% and 78.57%， respectively； 3） Compared with the infinite pile （L>20dp ）， the dynamic response of the lateral displacement and bending moment of the finite pile is more affected by the slenderness ratio L/dp； The maximum lateral displacement and bending moment of the pile increase with the increase of the amplitude of the horizontal harmonic load H0， and decrease with the increase of the dimensionless frequency a0.