Abstract: The following idea about the interaction between rigid body and soil are put forward in this paper.Under loads,a rigid body and the surrounding soil will change relatively their positions normal to or tangent to the faces of the rigid body.Since the rigid body can not be deformed,these positions changes can only be done by the deformations of normal compression or tangential bending of the surrounding soil .These two relative changes of position are not separated mutually,and can be interconnected by that the rigid body turns a little angle φ 0 round a special point (x 0,y 0). The paper deduces several groups of static equations depending upon the space static balance conditions of the rigid piles against sliding.Simplifing the equations and using them to the calculations of rigid foundations,the results of vertical pressure stresses are same completely with the traditional theory.