Meshing geological body with joints is one of the major difficulties of using FEM in slope stability analysis. The traditional method is to divide the body into simply connected domains and triangulation them. However, when the geological body has three groups of joints which are quite common in rock mass, the division and connection are quite complicated. In this article, a new meshing method is introduced. This method uses gravity force instead of geometry constrain to ensure mesh nodes lies on joint faces, and uses non-friction plastic particle to fill the geological body. After get the mesh nodes, constrained Delaunay triangulation (CDT) is used to get triangle or tetrahedron mesh. Joint recovery quality and meshing quality are checked with an example which has crossed joints.