Abstract: Monolayer microcrystalline diamond,nanocrystalline diamond and three-layer(the structure of films is micron layer(MCD)/nanolayers(NCD)/micron layer(MCD)) diamond films were deposited on Si substrate with H₂/CH₄/CO₂gas mixtures as source using microwave plasma chemical vapor deposition method respectively.The quality,surface morphology and grain size of diamond films were systematically characterized by Raman spectroscopy,scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results show that microcrystalline diamond with coarse grains and rough surface,nanocrystalline diamond with fine grain size and surface roughness,multilayer diamond films can be prepared by control of the reaction parameters in the growth process,can significantly reduce the surface roughness by the introduction of three-layer structure.