Abstract: 3D deformable distinct element method (3D DEM) is an efficient numerical tool for simulation of mechanical behaviors of discontinuous media. It is suitable to use this method to analyze problems of elasto-plastic, large deformation and dynamic systems because of the use of the explicit finite-difference scheme and the automatic contact detection method for discretized joints. Herein, the principles and features of the 3D deformable distinct element method were described and the failure process of Meihua Arch Dam in 1981 was simulated. It is evident that abutment thrust due to the reservoir load leads to the upward sliding of the dam along the peripheral joints due to the weak shear resistance of peripheral joints, thus causing the rapid collapse of the dam.