Abstract: Organic bentonite was prepared by using cetyl trimethylammonium bromide (CTAB) modified sodium bentonite. The adsorption properties of organic bentonite towards organochlorine pesticide chlorothalonil in waste water was investigated including pH values, temperature, adsorption time and amount of organic bentonite. The results showed that the removal rate could reach 82% when 0.30 g/L chlorothalonil solution was absorbed by 10 g/L organic bentonite for 30 minutes at 25 ℃ and pH = 7.