The vertical mineral combination of shale formations varies greatly, and shale gas exploitation requires large-scale artificial hydraulic fracturing. During the fracturing transformation of shale gas exploitation reservoir, the regularity and mechanism of permeability change are of great significance to the design of fracturing engineering of shale gas. Methods: The author and others conducted fluid-solid coupling physical experiments on three shale samples with different mineral combinations based on the whole-rock X-ray diffraction analysis of samples. Results: Shales with different rock and mineral compositions exhibit different characteristics of microfractures and permeability changes under different conditions. Both siliceous and carbonate minerals can be used as brittle minerals, but there are significant differences in their brittleness characteristics. Conclusions: Based on the comprehensive analysis, three insights were obtained: ① During the loading process, the presence of small stress platforms in the stress-strain curve can indicate the formation of micro-fractures in the sample, which is the intrinsic mechanism of permeability change; ② The permeability of different mineral combination shale samples varies significantly with the axial pressure. The essence is the combination of minerals, and the brittleness of shale samples is different. During the pressurization process, the development of fractures is different, resulting in different permeability changes; ③ Rickman's mechanical brittleness index can only better reflect the brittleness characteristics determined by siliceous minerals. While when the content of carbonate minerals (calcite) is high, Rickman's mechanical brittleness index is difficult to effectively reflect the brittleness characteristics.