Abstract: The main coal seam of Baode Coal Mine is a complex structural coal seam containing 5-11 layers of gangue, which poses technical challenges such as hindered vertical gas migration and low extraction efficiency. This study reveals the differential storage and permeability mechanism of coal seam gangue gas through multiple methods such as expansion experiments, XRD mineral analysis, permeability testing, and scanning electron microscopy observation. The results show that the mineral composition of the gangue is mainly kaolinite, and its water swelling rate is much higher than that of the coal seam. The permeability is only 1/134 of the parallel bedding direction of the coal seam. The interlayer impedes the vertical migration of gas through the combined effects of physical sealing, dynamic sealing, and capillary sealing; The triple sealing mechanism has led to the formation of isolated high gas units in coal seams separated by multiple gangue layers. Based on this, a large-scale hydraulic fracturing technology is proposed to improve the overall gas extraction efficiency. The research results provide theoretical and technical support for efficient gas extraction from complex coal seams in Baode Coal Mine.