based on the finite element method of superstructure-the pile raft foundation-the foundation soil action and interaction are studied. Research shows that the common function is considered, fundamental overall settlement and differential settlement with the increase of floor of a nonlinear trend. The influence of superstructure form is bigger for raft stress, the upper structure existing in secondary stress, and the bending moment and axial force than conventional design method slants big; With the increase of the floors, pile load sharing ratio is reduced gradually,but soil load sharing ratio is increased. Along with the increase of the upper structure stiffness, the load focused on corner and side pile; Increasing thickness of raft, can reduce the certain differential settlement and foundation average settlement, thus reducing the upper structure of secondary stress and improving of foundation soil load sharing ratio, at the same time the distribution of counterforce on the pile head is more uneven under raft, thus requiring more uneven from raft stress, considering the piles under raft and the stress of soils to comprehensive determines a reasonable raft thickness, which makes the design safety economy. As the foundation soil modulus of deformation of foundation soil improvement, sharing the upper loads increases, counterforce on the pile head incline to average, raft maximum bending moment decrease gradually.