A set of boron-doped diamond (BDD) electrodes were deposited on silicon substrates by direct current plasma chemical vapor deposition (DC-PCVD) system using different carbon source concentrations. The influence of carbon source concentration on characterization of BDD electrodes was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and phenol degradation. It was found that BDD films with different carbon source concentrations were polycrystalline films with (111) dominant orientation. The films grew well when carbon source concentration was less than 2.5%, while graphite phase began to form when carbon source concentration was increased to 3%. Boron atoms were located at the substitutional site or interstitial sites in the crystalline lattice of diamond films, and didn’t damage the structure of diamond crystal. Within 4 h, 100 mg/L phenol solution in 80 ml could be oxidized by all the electrodes with removal efficiency higher than 90%.