Abstract: Ultrasonic grinding pretreatment is applied on Cu substrates to deposit microcrystalline diamonds with self-nucleation method by hot filament chemical vapor deposition(HFCVD). It is show that without ultrasonic grinding pretreatment,only a few microcrystalline diamonds can be deposited on the Cu substrate. When the duration of pretreatment is about 1 min,a large amount of microcrystalline diamonds is deposited on the substrates simultaneously. However,when the duration of pretreatment is more than 2 min,too many diamonds are deposited and there forms a diamond film on the substrate. The microcrystalline diamonds deposited by CVD methods exhibit a cubo-octahedral morphology and have the euhedral diamond faces with(111) and(100).