Abstract: In order to find out the leaching difference between silica (quartz and cristobalite) and silica solid solution (quartz solid solution and cristobalite solid solution), the alkaline leaching kinetics of quartz and cristobalite with sodium hydroxide (NaOH) solution was studied in this paper, and the solubility difference between quartz and cristobalite was verified with the analysis method of transmission electron microscope. The results show that quartz violently reacted with NaOH solution at ≥180 ℃, while cristobalite quickly dissolved into NaOH solution at ≥130 ℃. The leaching of quartz and cristobalite in NaOH solution was controlled by surface chemical reaction, and their activation energies were 9.26 kJ∙mol⁻¹ and 5.02 kJ∙mol⁻¹, respectively. Quartz had the crystal characteristics of short-range order and long-range order, while cristobalite had the crystal characteristics of short-range order and long-range disorder. Thereby, cristobalite was more readily soluble than quartz in NaOH solution.