Diamond thin films were prepared by using chemical vapor deposition. It is enhanced to etch the sp2 bonding carbon atoms of the film by intermittently closing the methane gas during the deposition. These films were characterized by Raman spectroscopy and microscopy. The results show that the enhanced etching of sp2 bonding carbon atoms has no obvious effect on quality and microstructure of the diamond films. It reveals that the sp2 bonding carbon atoms do not mainly exist in graphitic or amorphous carbon grain form in the films but mainly among the carbon atoms of diamond grain surface or grain boundary.