A study is made of the forming theories and the computer aided design of the rotary cutting burs, for the purpose of finding the movement of the machining system and the corresponding sectional curvature of the groove conveniently. The equation of the cutting edges on the tool surface is deduced in this paper. The contact condition between the cutting edge of the tooth of the cutter and the grinding wheel is found, and the equation of the contact condition is deduced as well. Then the section line of the cutting edges of the rotary burs after CNC controlled machining is calculated. The research is useful for the programming of the CNC grinding on the CNC controlled machine tool.