Cemented carbide (WC–Co) is applied as the substrate instead of conventional ones such as Si, Ti, and Nb, on which nanocrystalline BDD films are deposited by hot filament chemical vapor deposition. Then the WC–Co/BDD electrodes are investigated by Field Emission Scanning Electron Microscopy (FE-SEM), Micro-Raman Spectroscopy, X-ray photoelectron spectroscopy (XPS), a four-point probe method, accelerated life test (ALT), and electrochemical analysis. According to the results, the BDD films deposited on the WC–Co substrate are highly uniform and pinhole-free with a grain size of 100 nm and a low compressive stress. The WC–Co/BDD electrode has a wide potential window of 3.8 V and low background currents in 0.5 mol L⁻¹ H₂SO₄ electrolytes and shows a quasi-reversible behavior in the K₃[Fe(CN)₆] redox system. The electrode has a service life of more than 400 h in the ALT with 3 mol L⁻¹ H₂SO₄ electrolytes at a constant current density of 1 A cm⁻². These electrochemical performances of BDD films on the WC–Co substrate is similar to or even slightly better than that on the commonly used substrates. Finally, phenol is used as a pollutant to test the activity of the WC–Co/BDD electrode. The results of replicated experiments show that the average COD reduces from the initial 5795 to 85 mg L⁻¹, and the average current efficiency is about 46%. This suggests that the WC–Co/BDD electrode has a good mineralization capacity in phenol with a high concentration.