Abstract: Connection of poorly sealed boreholes to an aquifer poses a threat to the safety of coal mine production. Taking the hydrological hole X5-3 of Xuchang coal mine in Shandong Province as the research object, the technology of underground opening and sealing was optimized, the high pressure grouting method was used to seal the lime-fly ash fissures, and the location of X5-3 borehole was found along the belt of 1337 working face through drilling and roadway exploration. The grouting pressure of the final hole was 8 MPa, lasted 30 minutes and 6,000 kg of cement were used totally, underground sealing and plugging were successfully realized. The application of underground opening technology not only ensures the safety of coal mine production and avoids the influence of water damage, but also reduces the engineering cost, which has reference significance for the same type of borehole opening.