The development and use of CAD system specifically for the geological drilling cone bit design with Auto CAD as its development platform is described. The system consists of three parts: parameter design, teeth arrangement design, and parametrical drawing, the computer aided design of geological cone bits can be performed by the use in menu, dialogue boxes and pictures. With the parameters selected, the teeth arrangement is designed, then the parametrical drawing is carried out to make the cone leg drawing, cone drawing and other parts' drawing; and finally make the assembly drawing.