In this work, DLC films are prepared by DC-pulsed PECVD after the oxynitriding treatment of V4E high vanadium tool steel. The experimental design includes various power densities (200, 400, 600 and 800 mW·cm⁻²) with an unbalanced bipolar-pulsed voltage. The deposition time is 90 min, and the CH₄ gas flow is maintained at 5 sccm, respectively. The experimental results show the duplex coating layers to have better properties when the DLC films are treated by an appropriate power density (400 mW·cm⁻²). These films also possess the lowest wear loss volume (for loads of 2 N and 5 N of 6.23 × 10⁻³ mm³ and 1.19 × 10⁻² mm³, respectively), the lowest corrosion current (4.09 × 10⁻⁴ A·cm⁻²) and the highest polarization resistance (258.83 Ω·cm²) after the 3.5 mass% NaCl corrosion test. This study confirms that the wear and corrosion resistance of V4E tool steel can be effectively improved through the DLC/oxynitriding duplex treatment.