The　chemistry　organobentonites　were　synthesized　by　means　of　the　ionexchange　reaction　between　single-octadecyl　trimethyl　ammonium　chloride(SOAC),　di-octadecyl　dimethyl　ammonium　chloride　(DOAC),　tri-octadecyl　methylammonium　chloride　(TOAC)　quaternary　ammonium　salts　and　sodium　base　bentonites,　respectively.　The　authors　used　FTIR,　X-ray　diffraction　diagram　and　DSC　thermograms　to　characterate　the　structure　of　the　modified　bentonites,　and　discussed　the　effect　of　different　quaternary　ammonium　salt　on　the　properties　of　organobentonites.　The　results　showed　that　ion　of　the　surfactants　had　entered　into　the　chip　layer　of　the　bentonites,　and　changed　the　hydrophilic　environment　of　the　chip　layer　into　hydrophobic　environment　and　increased　the　distance　among　the　chip　layer,　all　of　these　had　laid　a　base　for　the　preparation　of　the　nanometer　composite　material　of　high　polymer/bentonite.