Fourier Transforrn Infrared (FTIR) Spectroscopy and Wide Angle X-ray Diffraction(WAXD) techniqueS were used to study a selective modification of montmorillonite with hydroxyl group(一OH) of toluene-2,4-di-isocyanate (TDI)．Based on the investigation results,a schematic model was presented.The selective modification product was applied to prepare an intercalated polystyrene／montmorillonite nanooomposite,and the nanocomposite was characterized by WAXD and Tmnsmiesion Electron Microscopic (TEM) techniques．The FTIR results showed that after modification of cetyltrimethylammonium bromide(CTAB) exchanged montmorillonite,TDI was successfully selectively grafted to the surface—OH group of the rnontmorillonite via two different synthetic routes．And the WAXD results revealed that the interlayer distance of the montmorillonite was increased dramatically．Combining with the previous nvestigations, it mav be deduced that the orientation of the CTAB might be changed from a bilayer structtire parallel to adiacent silicate layers in CTAB-exchanged montmorillonite to a double layer inclined。tructure in the interlayer space of the TDI grafted montmorillonite product．The TDI modified montmorillomte product could be successfully applied to obtain an intercalated polystyrene／montmorillonite nanocomposite During the intercalative polymerization process,the interlayer distance of the TDI modified montmofillonite was increasedfurther．Five sharp diffraction peaks,d001=4 24,4．60,5.07,6.59,7.48nm,appeared for the polvstyrene／TDI modified montmorillonite nanocomposite The TEM investigation indicated tat the thickneSs of the montmorillonite primary particles was reduced to 20～50nm in the polystyrene matrix.The WAXD and TEM results suggested that an intercalated polystyrene／TDI modified montmorillonite nanocomposite was suceessfully achieved．