Abstract: Under potentiostatic model and by using activated carbon fiber (ACF) as anode or cathode respectively, the decolorization behavior of Reactive Blue 19, one of anthraquinone dyes, was studied in a two-compartment cell separated by cation exchange membrane. The linear sweep voltammograms of ACF in the dye solution were measured, and the relationships between color/TOC/COD_Cr removal ratio and electrode potentials were investigated. The results show that: (1) The onset reduction potential and the onset oxidation potential were -0.7 V and 0.5 V respectively; (2) In the range of -0.6—0.4 V, the decolorization results from adsorption of the dye on ACF, and adsorption behavior was scarcely affected by potential; (3) In the range of -1.5—-0.7 V, the electro-reduction of the dye played an important role in decolorization which followed pseudo-first order kinetics; (4) In the range of 0.5—1.6 V, the electro-oxidation of the dye played the role of decolorization which followed pseudo-first order kinetics, too.