Abstract: Existing sealing materials are limited due to their high price, curing shrinkage cracking, and insufficient compressive strength. This study therefore develops high-performance sealing materials to seal gas extraction boreholes and improve the life of gas extraction boreholes. We characterized the pore structure of high-fluidity slurry materials and ordinary mining sealing materials by ultrasonic detection method and low-field nuclear magnetic resonance to investigate the mechanism of high-fluid slurry materials in terms of porosity and ultrasonic attenuation coefficient. The properties of slurry materials were then verified in the field. Results show that after the grouting treatment of high-fluid slurry materials, the primary fractures and pores in the coal body became smaller, which effectively sealed the cracks in the coal body, stabilized the structure of the coal body more stable, and reduced the generation of air leakage channels. With the original process unchanged, plugging the gas drainage borehole with high-fluid slurry, the gas concentration of high-fluid slurry increased by more than 50 % and the extraction efficiency is significantly improved compared with that of ordinary cement materials.