Organobentonites　were　prepared　to　improve　the　compatibility　between　bentonites　and　organic　phase.　The　change　of　lamellar　structure　after　organic　modification　was　observed.　Na+-bentonites　and　octadecylamine　were　used　to　exchange　the　Na+　which　is　in　the　layers　of　bentonites,　and　the　organobentonites　were　obtained.　Both　FTIR　and　DTA-TG　proved　that　octadecylamine　entered　the　layers　of　bentonites,　and　XRD　showed　that　the　lamellar　distance　increased　from　1.4　nm　to　4.3　nm.　Based　on　the　experiment,　most　of　the　properties　of　Na+-bentonites　such　as　the　ethylene　blue　adsorbed　by　bentonites,　cation　exchange　capacity　and　the　like　are　better　than　Ca2+-bentonites＇.　The　bentonites　modified　by　octadecylarnine　improved-the　hydrophobic　ability　and　widened　the　lamellar　distance　of　bentonites,　which　contributes　to　enhancing　the　whole　properties　of　composites.