Abstract：Discrete element numerical methods are based on isolated block model of jointed rock mass. In this paper，some typical problems and difficulties of discrete element numerical methods are studied so as to obtain clearer and deeper understanding to them. The problems and difficulties are associated with various algorithms of discrete element numerical methods and their peculiarities，deformation，overlap between blocks，contact detection(including that of three-dimensional problems)and equation solving(especially the inherent relation between the single-block-equation solving and the whole-equation solving). Some helpful and meaningful results are obtained.
