Disclosed is an electrocatalytic oxidation reactor, which relates to the field of sewage treatment. The electrocatalytic oxidation reactor comprises a housing; an water inlet pipe arranged at the upper end of the housing; a water distribution device connected to the water inlet pipe, arranged in the housing, and near the top end of the housing; a filler layer arranged in the housing; electrodes arranged on side walls of the filler layer of the housing; an water outlet pipe arranged at the bottom of the housing; an aerating device arranged near the bottom of the housing; a layer of filtering cotton arranged below the water distribution device, wherein the filtering cotton is fixed and covers a first grid-shaped plastic frame; a second plastic frame is arranged below the first plastic frame and on the top end of the filler layer; a water stabilizing layer is formed between the first and second plastic frames; and a third plastic frame is arranged at the bottom of the filler layer, wherein the aerating device is arranged below the third plastic frame. The reactor is simple in structure, uniform in water distribution, high in current efficiency, large in treatment capacity, and low in energy consumption.