Montmorillonite was modified by chlorosilane derivatives (trimethylchlorosilane and tert butyldimethylchlorosilane) bas~ed on the reaction between OH group and chlorosilane. Fourier transformed infrared spectra (FTIR) confirmed that chlorosilanes did react with the OH groups of montmorillonite. The effect of reaction time and dispersing agents on the intercalation was studied by wide angle X ray diffraction (WAXD) method. Further experiments proved that there is no reactive OH group on the surface of layers in the interlayer galleries of montmorillonite. The cation exchange capacity (CEC) of montmorillonites was measured, showing that after modification by chlorosilane derivatives, CEC values drastically decreased. The dispersibility measurements of montmorillonites were conducted, which showed that the dispersibility of modified montmorillonites both in H 2O and toluene were improved due to the decrease of attractions of particles and layers. Montmorillonite was modified by chlorosilane derivatives (trimethylchlorosilane and tert butyldimethylchlorosilane) bas ~ ed on the reaction between OH group and chlorosilane. Fourier transformed infrared spectra (FTIR) confirmed that chlorosilanes did react with the OH groups of montmorillonite. The effect of reaction time and dispersing Agents on the intercalation was studied by wide angle X ray diffraction (WAXD) method. Further experiments that there is no reactive OH group on the surface of the layers in the interlayer galleries of montmorillonite. The cation exchange capacity (CEC) of montmorillonites was measured , showing that after modification by chlorosilane derivatives, CEC values ​​drastically decreased. The dispersibility measurements of montmorillonites were both in H 2O and toluene were improved due to the decrease of attractions of particles and layers.