Abstract: In view of the problems of gas overrun and coal and gas outburst accidents in the construction of underground gas extraction boreholes in coal mines, the problems existing in the traditional simple orifice device and the normally open automatic orifice prevention system were analyzed, and the normally closed blowout prevention system and method were proposed, which could be integrated with the drilling rig body to meet the needs of various special-shaped roadway orifice sealing, slag discharge and gas extraction. At the same time, the control system can be linked with the hydraulic control system of the drilling machine to realize the automatic closing of the pressure relief of the blowout prevention system at the orifice to prevent the leakage of gas in the hole. Compared with the traditional and existing orifice blowout prevention systems, the blowout prevention system is simple and clear, has stronger adaptability to the drilling rig, significantly improves the effect of drilling blowout prevention and treatment, and significantly reduces the labor intensity of workers, which can provide a favorable guarantee for the safety and efficiency of underground gas extraction drilling construction.