Abstract: As a kind of drilling devices, the drill tool is widely used in fields such as mining, transportation, geology and energy. The thermal treatment is one of the most important processes at quarantees quality. In the devolepment of this kind of drill stems, factors such as carburization techniques, time and depth, have been selected for study and an ideal curve has been obtained for gas carburization at three sections. The application of this curve to the carburization of drill stems could shorten one quarter of the time needed by ordinary techniques. Moreover, the carburization speed could increase 1. 2～1. 5 times and one third of kerosene could be saved. This technique effectively controls the oildropping amount and carburization time. As this guarantees the carburization quality. the wear and life drill stems are greatly improved.