4-Nitrophenol was decomposed by Fenton’s reagent in a flow electrochemical reactor, and the effects of Fenton’s reagent dosage, molar ratio of Fe(Ⅱ) to H2O2, initial pH, and H2O2 feeding time on the removal rate of 4-nitrophenol were investigated.The reaction system was modeled as a plug flow reactor (PFR) in series with a continuous stirred tank reactor (CSTR), and the pseudo-first order rate constant of 4-nitrophenol removal was determined from the model.The pseudo-first order rate constant increased with the increase of Fenton’s reagent dosage at a fixed molar ratio of Fe(Ⅱ) to H2O2, but decreased with the increase of H2O2 feeding time at a fixed Fenton’s reagent dosage.There existed an optimal molar ratio of Fe(Ⅱ) to H2O2 or initial pH for the pseudo-first order rate constant of 4-nitrophenol removal.