Korean montmorillonite was intercalated with Al-hydroxypolycation solution aged for 1, 4 and 7 days and then calcined at 400 ℃, 600 ℃ and 760 ℃, respectively. Basal spacings by XRD, pore structure (micro- and mesopore distributions and surface areas) by nitrogen (or argon) adsorption at liquid nitrogen (or argon) temperature and acidity (distribution and acid-amount) by NH3-TPD were investigated for the samples. The basal spacing formed by intercalation appeared at about 17 Å and decreased with the heating temperature for the sample intercalated with the Al-hydroxypolycation solution aged for 1 day. However, for the one aged for 7 days, the spacing remained constant. The total surface area and pore-volume also increased with aging time of the Al-solution, in which micro-pore area increased more rapidly. Argon adsorption indicated that three modal distributions of 3.3, 3.7 and 4.3 Å in micropore radius appeared, in which 3.3 Å readily was reduced by heating. NH3-TPD showed that two ammonia-desorption peaks appeared at 230 ℃ and 430 ℃, respectively. The maximum acid-amount for the intercalated sample appeared as 86 meq./100 g-solid, and the values decreased with the heating temperature, especially for the peak at 430 ℃.