In order to investigate the responses of laterally loaded single piles and the principle of the pile-soil interaction, the deflection curve differential equation based on the three-parameter method was introduced. Based on the pre-existing analytical solutions for laterally loaded piles in which the coefficient of subgrade reaction was assumed to be a constant and the continuity principle of pile responses, the semi-analytical solutions were submitted. The relevant computer program was developed by Fortran programming, and the obtained solutions were verified by comparing them with the pre-existing solutions corresponding to a special case.The calculation results indicated that the boundary condition at the pile tip plays a marginal role in pile responses when the pile length is comparatively great,the influences of two parameters from the coefficient of subgrade reaction, including the index and the parameter which represents the ability of soil at the ground surface to resist the lateral deflection on pile responses are too great to be ignored, and the obtained solutions are effective and can be applied widely.
