Abstract: In order to analyze the influence of sealing material properties on borehole sealing during grouting sealing in the sealing section of gas extraction borehole, special cement-based sealing materials were collected from different mining areas, and their viscosity, expansion rate, water separation rate, setting time and strength parameters after solidification were tested in the laboratory. The influence of the above indexes on borehole sealing was analyzed from the whole process of grouting in the early stage to solidification sealing in the later stage. The results show that the viscosity of the slurry is the key index to measure the fluidity of the grouting material in the early stage of the grouting. The faster the viscosity of the slurry rises and the faster the fluidity decreases, the more difficult it is to seal the cracks in the surrounding rock of the borehole. After the completion of the grouting in the middle stage, different materials show expansibility and water tightness. The expansion characteristics of the materials can provide support for the surrounding rock of the borehole and improve the stability and integrity of the heterogeneous structure of the sealing section of the borehole. Water tightness of the materials will cause the separation of the borehole wall surface from the sealing material, increase the air leakage channel and reduce the water tightness. The strength of the sealing material after solidification at later stage is greatly different from that of the coal body, forming unstable heterogeneous structure. Under the action of stress, the fracture of the unstable heterogeneous structure develops and the tightness decreases.