Abstract: According to the character of the interface between soil and pile in the dynamic soil-pile interaction, the constitutive relationship of a new planar contact model considering the effect of separating, sliding and pile uplifting is presented, and associated element stiffness matrix of interface element is deduced. Then the problem describing the energy dissipation of interface element during dynamic interaction is solved by adding the damping component, and method of determining the thickness of interface element is proposed. Compared with the Goodman element, the seismic response (acceleration, displacement) of superstructure obtained by use of the planar contact model under moderate earthquake is reduced. Thusly, the planar contact model can simulate the effect of separating, sliding and pile uplifting in the dynamic soil-pile interaction under strong earthquake.