Abstract:  In order to study the influence of the genetic characteristics of Li，Na，K-based montmorillonite on the hydration swelling characteristics，using the lithium chloride，sodium chloride，potassium chloride type of centrifugal purification after Wyoming sodium montmorillonite modification processing，preparation of Li，Na，K montmorillonite samples，and the hydration swelling test，after using ICP，FTIR，XRD，NMR methods to analyze the Li，Na，K element content of montmorillonite，the type of functional groups，under the state of hydration swelling，layer spacing changes and moisture state. Results show that Li based montmorillonite hydroxyl stretching vibration peak and hydroxy bending vibration peak strength higher than that of Na and K based montmorillonite，modification of montmorillonite hydration swelling capacity from strong to low order as: Li base＞Na base＞K base，Li，Na，K montmorillonite in the condition of hydration swelling are bound water and free water moisture，moisture content to include: Li base＞Na base＞K base，after hydration swelling，the layer spacing of Li base increased the most，while that of K base montmorillonite increased the least. This conclusion provides an important theoretical basis for revealing the mechanism of internal water occurrence and comprehensive utilization of montmorillonite.

Key words: Montmorillonite, Modification, Hydration swelling