Abstract: This Paper aims at studing the interaction between the inverted-siphon of the Diverting Water From South To North and the foundation. The material character of the inverted-siphon is very different from that of the foundation. Therefore, on certain condition slide or split will happen on the contact face. To reflect the character of contact face, a special joint element should be adopted. In this paper, a three dimensional joint element model is used to probe into the interaction. and the structured programming technique is adopted to program the calculating software of three dimensional joint, which well solved the interaction problem of the structure and foundation, and supplies the sufficient theory base for the safety design of the inverted-siphons.