<p>Extracting Al from coal gangue has the double benefits of realizing the high-value application of coal gangue and mitigating the scarcity of bauxite resource. The key Al-containing minerals in coal gangue include kaolinite and boehmite, and thermal activation is pivotal for stimulating their reactivity. In this study, kaolinite and boehmite were subjected to thermal activation and acid leaching to explore the intrinsic link between their thermal evolution and leaching activity. Results showed that the phase evolution of kaolinite followed a multi-step sequential process in the order of kaolinite → metakaolinite → <i>γ</i>-Al₂O₃ → mullite, and Al^V in metakaolinite was highly active. For boehmite, it underwent the transformation of boehmite → <i>γ</i>-Al₂O₃ → <i>δ</i>-Al₂O₃ → <i>θ</i>-Al₂O₃ and <i>α</i>-Al₂O₃ successively. Their reactivity in descending order was <i>γ</i>-Al₂O₃ &gt; <i>δ</i>-Al₂O₃ &gt; boehmite &gt; <i>α</i>-Al₂O₃. Furthermore, a comparative study of leaching temperature demonstrated that elevated temperature favorably strengthened the thermodynamic driving force and greatly promoted the Al extraction. This study is of some theoretical significance for guiding the thermal activation and acid leaching of coal gangue.</p> Graphical Abstract <p></p>