Dissolution of kaolinite was investigated in pH5.5, pH4.5 and pH3.5 HAC/NH₄AC buffer solutions separately with the batch method at room temperature (25℃±1℃). The results showed release of Al and Si from kaolinite was enhanced significantly by proton, compared with that in deionized water. It decreased with increasing pH. Dissolution stoichiometry of kaolinite was related to pH. The process of kaolinite dissolution was apparently nonstoichiometric in pH5.5 due to Al-rich precipitation. Preferential Al-release was observed initially at pH4.5 and pH3.5, however, the release of Al and Si inclined towards stoichiometric after 936 h. The dissolution rates of kaolinite in pH5.5, pH4.5 and pH3.5 HAC/NH₄AC were 3.09×10^-14 mol/(m²·s), 6.31×10^-14 mol/(m²·s), and 1.13×10^-13 mol/(m²·s), respectively. The reaction order and rate constant of proton-promoted kaolinite dissolution were 0.28, 1.12×10^-12, respectively.