Activated carbon fiber couil be prepated at 973 K by cataytic activation using potassium hydroxide. Phenol resin fiber (Kynol) was impregnated with potassium hydroxide ethanol solution, carbonized and activated at 973 L, resulting in activated carbon fibers with different porosities. The potassium hydroxide acclerated the activation of the fiber catalytically to from narrow micropore preferentially in carbon dioxide atmosphere.