Abstract: Considering that there was dummy shear zone between pile-soil interface,the compatibility equation of pile-soil was built up with extended compatibility deformation equation based on displacement solution of Mindlin.It was assumed that pile was elastic,and there was relationship between shear stress and relative displacement a hyrerbolic at the pile-soil interface,then the equation was built up and solved by finite difference method.Relative displacement of pile-soil interface was simulated very well,and appropriate explanation of interaction of pile-soil was extracted.Finally some case histories were analyzed,the calculated and results measured agreed well with each other.