Abstract: Borehole grouting for sealing the holes is one of the main technical means for gas extraction, the quality of hole sealing directly determines the extraction effect. In order to improve the effect of grouting and plugging, the collected rock samples were drilled and slit, and the rock samples with different numbers of slits were grouted and plugged to make slit grouting specimens, and based on the coal-rock triaxial compression test system, triaxial compression mechanical test was carried out on the specimens to get the compression strengths of grouted specimens with different numbers of slits. The industrial CT scanning equipment was used to scan the compressed specimens to get the two-dimensional fracture network characteristics of the specimens after destruction, and AVIZO image analysis software was used to identify the CT scanning results of different specimens and analyze the two-dimensional development characteristics of the fracture of different specimens after compression, and at the same time, VG Studio MAX image analysis and processing software was used to carry out three-dimensional reconstruction, and analyze the number of slits and fracture rate of the specimens, fractal dimension and Euler number. The results show that: the data of slits directly affect the mechanical properties of the borehole grouting specimens, with the increase of the number of slits, the strength of the specimens is weakened; according to the industrial CT scanning results of the damaged specimens, the analysis of the development of the cracks, and the complexity and connectivity of the fracture network found that the slits have a guiding role in the expansion of fracture development of the load-bearing body, and the predominant angle of the development of pore cracks is ±45 °, and the development of cracks in this direction is more prominent; with the increase of the number of slits, the development of fractal dimension and Euler number are more prominent; the fracture rate and 3D fractal dimension increase linearly with the increase of the number of slits, while the Euler number decreases linearly with the increase of the number of slits in the boreholes. The grouting of slits in boreholes is conducive to improving the quality of hole sealing, but too many cut slits will deteriorate the quality of hole sealing.