Efficient and harmless disposal of landfill leachate has attracted increasing attention. In this study, the bio-electro-Fenton method was investigated and developed to degrade the organic compounds in landfill leachate by hydroxyl radical oxidation. The optimal operational parameters (i.e., pH and external voltage) of the bio-electro-Fenton system were detected. Under the conditions of pH 2, 0.6 V, the highest total chemical oxygen demand (COD) decrement efficiency was obtained (about 70%), with apparent removal constant at 6 h (k) of about 0.12 h. Subsequently, to further increase the degradation efficiency, functionalized carbon black and functionalized carbon nanotube (FCNT) were prepared as catalysts for the cathode electrode modification. With 0.4 mg/cm FCNT coated on the cathode electrode, 91.3% of the organic compounds were degraded, remaining only 84 mg/L COD (k = 0.24 h). In all the reactors, the COD was mainly decreased in 0-6 h, contributing to over 68% of the total degradation efficiency. In the bio-electro-Fenton system, the bio-anode electrode could enhance HO production and the conversion between Fe and Fe by strengthening electrons generation and transportation via the oxidation of organics by biofilms (dominant with Geobacter) covered on the carbon brush.