Abstract: Multi-body contact is a strong nonlinear problem. In recent years, computational contact mechanics has been well developed and applied gradually in geotechnical engineering. This paper presents a computational contact mechanics method and its application to 3D stress-deformation analysis of concrete diaphragm walls, along with a case study of the Hongshiyan landslide dam. Results show that this method is capable of handling calculations on a non-conforming mesh and well describing such deformation discontinuities as sliding and separating between a diaphragm wall and its surrounding soil. The calculated stress distribution in the diaphragm wall is reasonable and stable with no exceptional fluctuation or oscillation, implying that the proposed contact mechanics method is effective and applicable to the contact problems of this type.