Abstract: With bilinear load-transferfunction,a set of analytical equations for the axial loading-settle-ment curve of pile are established. Influences of the surrounding and underlying soils on the loading--settlement curves and the correlation of elastic stifftness with bearing capacity of pile are then discus-sed herein. This paper will be of practical significance in design of pile foundations and evaluation of thetheoretical basis and limitation for low-strain dynamic tests of pile.