Based on comparison and analysis on structural cations of montmorillonite in bentonite samples collected from several typical areas in Jilin Province，relationships among type and quantity of interlayer /tetrahedral /octahedral cations and temperature and activation energy of removal of bound and hydroxyl water were investigated． The results show that the interlayer cations not only play decisive roles on removal temperature of bound water，but also influence dehydroxylation temperature and activation energy of montmorillonite． Type of octahedral cations also has an effect on dehydroxylation process．