To uncover the key factors controlling shale CO₂ adsorption in the Huainan area, eight shale samples from the Lower Shihezi and Shanxi Formations in Bailitang were selected, and systematic CO₂ adsorption isotherm experiments were carried out. The adsorption mechanism was analyzed using the optimized Langmuir, Two-parameter Brunner-Emmett-Teller (DBET), and Dubinin-Astakhov(DA) models. The influencing factors were explored by total organic carbon (TOC), mercury porosimetry porosity, and mineral composition tests. Results show that shale CO₂ excess adsorption capacity first increases, then decreases, and finally stabilizes with pressure rise, while absolute adsorption capacity keeps rising to saturation. The optimized Langmuir and DA models fit excess adsorption better than the DBET model, and the optimized Langmuir model is more suitable for absolute adsorption. CO₂ adsorption phase density fitting shows a composite mechanism of monolayer and micropore filling adsorption. The theoretical CO₂ adsorption capacity is positively correlated with porosity, micropore volume, TOC, and clay mineral content, negatively correlated with feldspar content, and unrelated to quartz content. The research results provide a theoretical basis for evaluating the potential ofshale CO₂ storage and optimizing engineering parameters in the Huainan area.