Abstract: Montmorillonite-iron(Ⅲ)catalyst is prepared.By means of X ray powder diffraction and electron microscope the structural properties of the catalyst a re studied.Fe(Ⅲ) exists in the lager of montmorillonite-iron catalyst.The s tructure of montmorillonite has no change.The quartz composition in the cata lyst is about 22%～24%.The structural defecd of montmorillonite in EC1 and E C 2 is less than that of EC4,EC5 and EC6.The rate of transformation is hig h and the velocity is rapid when EC4,EC5 and EC6 are used as catalysts,at the sa me time the separation is simple and can be used repeatedly.