Abstract: In this article, Na-montmorillonite (Na-MMT) was modified by butyltriphenyl phosphoninm bromide ( BTPB ) and dodecyl triphenyl phosphonium bromide(DTPB).Sedimentation experiments showed that modified montmorillonite had better dispersibility and swelling property in organic solvent containing toluene and benzene. XRD and FTIR demonstrated that the quaternary phosphonium cationic had intercalated interlayer of montmorillonite and the interval distance of montmorillonite was obviously enlarged. TG curves show that the initial decomposition temperature of quaternary phosphonium modified montmorillonite rose by 102 C and 57℃，respectively, in comparison of that based on quaternary ammnnimm salt.

Key words: quaternary phosphonium salt, montmorillonite, intercalation modification