Abstract: Polycrystalline diamond films were deposited on the substrates of ceramic materials alumina by use of hot filament chemical vapor deposition (HFCVD)from a source of gas mixture of ethanol and hydrogen. The diamond films on the alumina substrates were observed by scanning electron microscopy (SEM) and optical microscopy (OM), and identified by low-angle diffraction analysis and Raman Spectroscopy. Structure and characters of diamond deposited by HFCVD can be influenced by the carbon concentration, tungsten temperature, substrate temperature and pretreatment technique. The best technology was obtained. The nucleation and growth mechanism of diamond films deposited on alumina has been discussed.