Abstract: Drilling jet orifice is a kind of dynamic phenomenon in the process of using high-pressure water jet cutting technology to enhance gas permeability of coal seams. Mechanism for drilling jet orifice was theoretically analyzed and protective measures were proposed. Field application was performed at the middle bottom roadway of Ji₁₅-24080 working face in the 10th mine of China Pingmei Shenma Group. The results show that: protective measures are fairly applicable and can be effectively used to prevent and handle dynamic phenomena such as drilling jet orifice etc. In the process of high-pressure water jet cutting, and the percentage of drilling jet orifice fell from 64.7% to 15.0%; the percentage of hold drill declined from 35.3% to 1.7%; the percentage of normal boreholes increased from 35.3% to 85.0%; all these ensure field work safely and orderly.