Abstract: Aiming at the technical problems of poor sealing performance, rapid decay of gas concentration volume in boreholes and high economic costs of sealing in traditional sealing technology, " a new sealing technology of “adaptive borehole deformation, flexible pressure holding, dynamic sealing and reuse” is proposed. A new type of “fetal sac type” reusable sealing device for gas drainage is developed, and the basic structure design and sealing technology principle of “fetal sac type” sealing device are expounded. The core component of the sealing device ( sealed fetal sac ) is systematically studied by means of numerical simulation, laboratory experiments and theoretical analysis. The results demonstrate that the fetal sacs with wall thickness of 1 mm and 2 mm can expand rapidly under lower grouting pressure , meeting borehole sealing requirements. The average contact pressure between the sealed fetal sac and the hole wall increases gradually with the increase of the applied force. Compared with the sealed fetal sac with a wall thickness of 1 mm, the sealed fetal sac with a wall thickness of 2 mm has a more stable overall sealing performance with the increase of the pressure. The results of the sealing experiment demonstrate that the ultimate bearing capacity of the fetal sac is positively correlated with the wall thickness of the fetal sac. When the grouting pressure is greater than 0.32 MPa, the sealing device can effectively seal the borehole. Combined with the results of numerical simulation, hole sealing experiment and mechanical analysis of grouting hole sealing, the optimal combination solution of the structural design parameters of the fetal sac is that the length is 1 000 mm, the wall thickness is 2 mm. The field engineering practice show that compared with the traditional “two plugging and one injection” pressure sealing process, in the same extraction period, the average gas extraction concentration volume of the new sealing process is 126.6% higher than that of the traditional sealing process, and the average extraction purity is increased by 120%. After the first extraction, the recycling rate of the fetal sac is 84%, and the recycling rate of the fetal sac is 65% after the third extraction, and the extraction concentration volume is increased by more than 30%. These results confirm that the new sealing technology not only enhances extraction efficiencyand prolongs the high concentration volume extraction time, but also achieves the effect of repeated utilization of the sealing device, provideing a new technical path for mine gas extraction methods.