The electrochemical behavior of a boron-doped diamond film electrode prepared by chemical vapor deposition was studied. The surface microstructure of the electrode was studied by means of scanning electron microscopy. The electrochemical behavior of the electrode was investigated by cyclic voltammetry and AC Impedance. The diamond films exhibited a “cauliflower-like” morphology and contained microcrystallites. The results showed the electrode having a very wide potential window and very low background current. The potential windows in acidic, neutral or alkaline medium were respectively 4.4[V], 4.0[V] and 3.0[V]. The background current was as low as -8×10-6～5×10-7[A]. In the electrolyte including Ferri/Ferrocyanide, the electrode surface kept good activity, and the electrochemical reaction occurring on the surface was a diffusion-controlled reaction, with good quasi- reversibility. Compared with Pt and graphite electrodes, diamond electrodes can oxidize compounds like phenol effectively, and the process of oxidization was very simple and complete.