Abstract: Gas drilling and extraction is one of the important means of gas control. In order to effectively improve the sealing effect of drilled holes, the influence of drilling grouting pressure on the sealing effect was studied. The permeability test and the scanning electron microscope (SEM) were carried out respectively under different grouting pressures by using the self-made grouting system; according to the results of SEM experiment, the tightness of the arrangement between the slurry particles and the cementation of the interface were analyzed. The results show that with the increase of grouting pressure, the permeability drop of the grouting borehole sample increases first and then decreases, and the mass increase gradually increases and tends to be the same, and the optimal grouting pressure is 1.2 MPa; the decrease of permeability and the increase of quality of the grouting material samples are negative exponential; the greater the grouting pressure is, the closer the arrangement between the slurry particles, and the smaller the probability of porosity.