A monolithic-porous carbon (MPC) was fabricated by carbonizing a pine rod, and then the oxidized monolithic-porous carbon (O-MPC) was obtained via alkaline heat treatment of MPC. With well-ordered axial channels (diameters were 6–14 μm and 40–50 μm) and oxygen-containing functional groups, O-MPC as a flow-through cathode exhibited good capability in continuously generating H2O2 (422 μmol/L) via oxygen reduction. O-MPC and additional Fe2+ composed an electro-Fenton system and the performance of the system in degradation of organic pollutants was evaluated. For phenol, bisphenol A or sulfamethoxazole at initial concentration of 10 mg/L the removal efficiency reached 74%–82% in a hydraulic retention time of 100 seconds, nearly close to that of the homogeneous Fenton process (90%). This efficiency may be maintained for at least 10 hours, indicating a good stability of O-MPC. The results demonstrate the potential of O-MPC as a flow-through electrode to realize homogeneous-like degradation of organic pollutants in wastewater.