In this paper, a simple method and procedure is given by which cone radius, journal angle, diameter and leg datum point size of a rock bit can be calculated respectively according to geometric relations of rock bit structure parameters. with the help of the method and procedure, the interrelationship of these geometric parameters can be quantitavely determined so as to Select optimum parameters. The procedure is written in Basic Language with a few words, so that the computation can be finissed in a short time by using a common pocket coraputer which is of lessstorage capacity .sad lower computing speed.Furthemore，the results obtained are accurate enough.
