This study was undertaken in an effort to select the sire bull in Hanwoo through in vitro fertilization of proven bull semen. It was used for in vitro fertilization that of the 20 proven bull semen with follicular oocytes derived from slaughterhouse ovaries of Hanwoo. The stage of maturation on the time course of bovine cumulus-enclosed oocytes incubated for 24 hours was found the highest(96.4%) than hose of other maturationi time. In vitro fertilization rate of bovine oocytes with proven bull sperm showed from 61.5 to 88.9%. Polyspermy of in vitro fertilized oocytes according to proven bulls were the highest KP 491(61.5%) nothing but KP 486, KP 491 and KP 497.