Abstract: As a significant type of dam on deep overburden, the earth core rockfill dam connects the concrete cut-off wall and soil core wall directly, and the "penetration" phenomenon with local large deformation may exist between cut-off wall and core wall due to the difference in material stiffness. Using an arbitrary Lagrangian-Euler (ALE) framework, an elastic-plastic meshless large deformation method is developed in this research. The meshless method has the benefit of flexible nodal distribution, and the ALE framework shows the advantage of accuracy and stability in large deformation analysis, thus avoiding the precision reduction or re-meshing procedure in the mesh-based large deformation method. The introduced approach is incorporated into the self-developed calculation platform GEODYNA and combined with the finite element method (FEM) and the scale boundary finite element method (SBFEM). Finally, the coupled meshless-FEM-SBFEM applied to an earth core rockfill dam on deep overburden, and combined with the generalized elasto-plastic model, the "penetration" phenomenon with local large deformation is simulated. The results indicate that the large deformation analysis can capture the stress distribution of the cut-off wall and the soil deformation near the joint zone more reasonably, the vertical stress of the cut-off wall calculated by the small deformation analysis is underestimated by about 4.1 MPa (13%), and a shear zone exists between the soil area at the top of the cut-off wall.