With the growing demand for the exploitation of unconventional oil and gas reservoirs, substantial advancements in fracturing fluid formulations are being achieved, significantly enhancing reservoir stimulation and resource recovery efficiency. The influence of fracturing fluids on the methane adsorption behavior of shale was examined through experimental investigations employing a custom-designed high-pressure adsorption apparatus. It was observed that the introduction of fracturing fluid reduces the methane adsorption capacity of shale while facilitating methane diffusion at low pressures. A pronounced decline in methane adsorption capacity was identified, with the maximum value reaching approximately 2 mL/g. Furthermore, under high-pressure conditions, fracturing fluids were found to inhibit methane diffusion, as indicated by a decrease in the diffusion coefficient with increasing pressure. Post-treatment analysis revealed significant alterations in the mineral composition and pore structure of the shale, including a reduction in the content of minerals such as plagioclase and dolomite, accompanied by a decrease in porosity. These findings offer valuable theoretical insights and empirical evidence to inform the optimization of fracturing fluid design and the improvement of shale gas recovery efficiency.