Since PDC（Polycrystalline Diamond Compact）was developed successfully in 1980s, PDC drill bit has been widely applied in petroleum drilling and geological exploration in many countries due to its good penetration ability and wear resistance, and very good results have been obtained. However, how to further improve its technical and economic indicators in drilling engineering becomes a very urgent problem. Russian doctor of technical sciences professor Скоромных В. В. and some others have studied this problem for many years and put forward an idea of stabilized mode of rock fragmentation, that is a rock fragmentation method under the condition that the resultant force R held together by axial load & torque sheering force and the cutting surface are perpendicular to the angle with the constant cutting depth. On this basis, some suggestions on PDC bit design are presented.