Using sodium-based montmorillonite as raw material and based on the potentiometric titration curve and characteristic critical point, the authors divided the transformation of Al³⁺ into four morphologies, and prepared the corresponding montmorillonite. X-ray diffraction, infrared spectroscopy and thermal analysis were used. The microstructure and thermal stability of pillared montmorillonite were studied. The results show that the d₍₀₀₁₎ value of pillared montmorillonite layer spacing in zone Ⅲ increases from 12.408 1 to 18.317 5 nm. Meanwhile, the strength of the Si-O stretching vibration peak of pillared montmorillonite in zone Ⅲ decreases obviously. The dehydroxylation reaction of octahedral structure of talc shifts to low temperature zone compared with that of original ore, which indicates that pillared montmorillonite in zone Ⅲ has bonding reaction and the pillared effect is the best.