Abstract: TMAB and CTMAB-bentonite(OMMT) were synthesized by inserting tetramethylammonium bromide(TMAB) and hexadecyl trimethylammonium Bromide(CTMAB) into the interlayer of bentonite mineral successively that had been purified and Na-modified.The structure of the modified bentonites was characterized by IR and X-ray diffraction.The Eriochrome Black T wastewater was decolorized by OMMT under experimental conditions.The decolorization ratio was investigated in terms of dosage of OMMT,reaction time,pH etc...