A range of activated carbons were prepared from sisal fiber with phosphoric acid activation.The produced activated carbons were characterized by Nitrogen adsorption isotherms and Scanning electron microscope to research the sisal fiber activated carbon.The results showed that sisal fiber is a good precursor for activated carbon.The optimal pretreatment and activation condition is: H3PO4 concentration 50%,impregnation ratio 1/1.5,activation temperature 400℃ and activation duration 90 min.Characteristics of activated carbon with a high adsorption capacity are: specific surface area (SBET) 1877 m2·g-1,total pore volume 1.87cm3·g-1,average pore width 4 nm,iodine number of adsorbent (Q iodine) 1051.1 mg·g-1,amount of methylene blue adsorption (Q mb) 217.5 mg·g-1,yield 35%.The study demonstrates that activated carbon prepared with H3PO4 activation has a high specific area and a large proportion of mesopores,which could be therefore universally applied in liquid-adsorption industry.Moreover,it has significant meanings to solve the pollution problem and promote economic development for the production place of sisal fiber.