Abstract: Diamond like carbon (DLC) films were deposited on Si(100) substrate by coupling DC and RF reactive magnetron sputtering. The deposition rate, the chemical structure, the surface roughness, the surface morphology and the mechanical property were studied. The thicknesses of DLC films were measured by the surface profiler technology. The chemical compositions of DLC films were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The mechanical properties of DLC films were investigated by nanoindentation techniques and the stress in DLC films was measured by substrate curvature method. The surface roughness and surface morphology were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. It is found that the deposition rate decreases, while the sp³ content in the DLC films increases with the hydrogen flow. When the hydrogen flow is at 25 mL/min, the sp³ content reaches 36.3%, and the hardness and modules of films reach the maximum value of 17.5 GPa and 137 GPa, respectively. The internal stress of DLC films prepared at different hydrogen flows is less than 0.5 GPa. The coupling DC and RF reactive magnetron sputtering may be really an effective method to prepare high quality thick DLC films with low internal stress. When the hydrogen flow increases, the surface of the DLC films becomes denser and smoother, the surface root mean square roughness decreases from 5.40 nm to 1.46 nm.