The montmorillonite was studied by differen t methods, such as chemical analysis, DAT, TG, X RD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octa hedra sheets begins dehydrating when the thermal treatment temperature reaches 659℃, but th e layer structure remains the same,and the corresponding Al(Ⅵ) is turned into Al(Ⅳ) in octahedra sheets. When the temperature reaches 900℃, the layer struct ure of montmorillontite is destroyed, and the new mineral phase μ-cordierite i s found. When the temperature reaches 1200℃, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase.Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅵ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350℃, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR. The experimental results show that the hydroxyl in octa hedra sheets begins dehydrating when the thermal treatment temperature reaches 659 ° C., and the chemical composition of the montmorillonite was studied by differen t methods, such as chemical analysis, DAT, TG, X RD, IR, AFM and MAS NMR when the temperature reaches 900 ° C., the layer struct ure of monmormorite is destroyed, and the new mineral phase μ- When the temperature reaches 1200 ° C, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase. Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅵ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350 ° C, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appears, corresponding to Fe- cordierite spectrum in XRD and MAS NMR.