Abstract: The influence of mechanical properties of the sealing material and grouting parameters on the coupling deformation of coal-sealing material in the sealing section of gas extraction borehole is still unclear, which is the main factor restricting the improvement of sealing performance of deep coal seam borehole. Based on the structural characteristics of coal-sealing material in borehole sealing section, by introducing the coupling strength factor χ of coal-sealing material, the coupling mechanical model of coal-sealing material in borehole sealing section was established by using Mohr-Coulomb criterion. The analytical solutions of the stress, displacement, plastic zone radius and fracture zone radius of the sealing material and coal were derived, and the calculation method of the leakage area in borehole sealing section was obtained. Then, the influence of the factors such as the cohesion of the sealing material, the supporting force and borehole radius on the radius of plastic zone and fracture zone of coal-sealing material in the sealing section was studied. The effects of supporting force, cohesion of sealing material and coupling strength factor χ of coal-sealing material on the leakage area and sealing performance of borehole were discussed. The mechanism of coupling strength factor χ of coal-sealing material affecting borehole sealing performance was clarified. Then, the numerical simulation method was used to verify the total plastic zone area of the coal-sealing material in the sealing section. Finally, the field test and theoretical calculation results of the total leakage area were compared and analyzed through the gas extraction borehole sealing engineering practice. According to the variation law of gas extraction pure volume and gas extraction concentration, the optimization scheme of borehole sealing parameters was proposed. The results showed that the cohesion of the sealing material, the supporting force and the borehole radius had little influence on the radius of the fracture zone of the sealing material, but had a great influence on the radius of the fracture zone of the coal. The leakage area of the coal in the sealing section was significantly larger than that of the sealing material, and the factors such as the cohesion of the sealing material, the supporting force, the borehole radius and the coupling strength factor χ of the coal-sealing material had a greater influence on the leakage area of the coal. The area of coal leakage area was the main factor affecting the sealing performance of borehole. With the increase of the cohesion of the sealing material, the supporting force and the coupling strength factor χ of coal-sealing material, the leakage area of the coal decreased and the sealing performance of the borehole was improved. The coupling strength factor χ of coal-sealing material was related to the elastic modulus and Poisson’s ratio of the sealing material, When \dfracE_\mathrmn\mu _\mathrmn > \dfracE_\mathrmm\mu _\mathrmm, the constraint stress factor λ of the sealing material to the coal was greater than 0, and the coal was compressed and deformed in the contact zone. At this time, χ>1, resulting in an increase in the ultimate compressive stress borne by the coal in the contact zone, which led to the decrease in the radius of the coal fracture zone and the leakage area, and the improvement of the sealing performance of the borehole. The larger the elastic modulus of the sealing material and the smaller the Poisson’s ratio of the sealing material, the higher the sealing performance of the borehole. The simulation results of the total plastic zone area and the field test results of the leakage area were basically consistent with the theoretical calculation results, and the theoretical model had high reliability. Based on the analysis of gas extraction pure volume and gas extraction concentration, it is proposed that when the borehole radius is 47 mm, the sealing material with coupling strength factor of 1.25 and cohesion of 1.5 MPa should be selected, and the grouting sealing pressure should not be less than 1 MPa. When the borehole radius is 56.5 mm and 66.5 mm, the sealing material with coupling strength factor of 1.46 and cohesion of 2.5 MPa should be selected, and the grouting sealing pressure should not be less than 1.5 MPa, which provides a strong guarantee for ensuring the sealing performance of the borehole.