In this study, pentachlorophenol (PCP) was degraded by the electroenzymatic method, which combines the enzymatic catalysis and the electrogeneration of hydrogen peroxide (H2O2). The experiments were conducted in a two-compartment packed-bed reactor using horseradish peroxidase (HRP) immobilized electrode. The highest production of H2O2 and the current efficiency were observed at .0.4 V vs. Ag/AgCl and a flow rate of 1 mL/min. The highest initial degradation rate and degradation efficiency of PCP were achieved at pH 5 and 25 oC. Under the conditions, the electrolysis was compared with an electrochemical method. The presence of chloride ion indicates that PCP was dechlorinated at the initial period of degradation. According to the proposed breakdown pathway and the intermediates, the electroenzymatic method showed an improved degradation ability compared to an electrochemical method.