Diamond films were deposited on metal copper substrate with a buffer layer of titanium with the mixture gas of methane and hydrogen by hot filaments chemical vapor deposition ( HFCVD) . Effects of different thickness of titanium layer on diamond films by HFCVD were investigated. The components of films were investigated using X-ray diffraction ( XRD) and laser Raman spectrum, and the surface morphology and structure were observed by scanning electron microscopy ( SEM) . The surface element of samples processed by heat treatment were analyzed using energy disperse spectroscopy ( EDS ) . The results show that when the thickness of titanium layer is 3 μm, the diamond film breaks down due to large internal stress. When the thickness of titanium increases to 25 μm, the diamond film is good and don爷 t break down with the existence of internal stress in the membrane. The diffusion between copper and titanium happens when the sample is processed by heat treating at 850 ℃ for