Micro-Raman analyses were carried out to investigate the micro-structure of cross section for diamond films prepared by hot-filament chemical vapor deposition.The variation of Raman peak feature with position was recognized as the difference of micro-structure in the film.The presence of broad band and high background intensity near the substrate surface was attributed to the amorphous carbon synthesized in the nucleation process of diamond film.The reduction of sp3-bond structure in the amorphous carbon phase was used to account for the observation of the 1200—1600cm-1 band intensity declination as the increase of film thickness.From the Raman feature it was shown that the sp2-bond structure and the graphitic phase decreased slowly,compared with the bond structure in the growth process of the film.The micro-Raman spectroscopy obtained by scanning parallel to the surface of the film showed the structure and composition difference between the diamond grain and the grain boundary.