The DDA method parallels the finite element, which solves a finite element type of mesh where all the elements are bounded by discontinuities. In the current studies on the DDA method, the deformation of all the discontinuities is neglected, only the deformation of blocks is concerned with. The actual engineering indicates that the deformation of control discontinuity is often greater than that of block, and can not be neglected; but the deformation of the smaller discontinuities may be neglected. In this paper, the deformation of discontinuity is studied, and the result indicates that the displacement and stress of block element are affected by the deformation of discontinuity to a degree. Therefore, the deformation of control discontinuity can not be neglected in the study of the DDA method.