The metallic films covering diamond play a very important role in the course of diamond nucleation and growth from Fe-Ni-C system at high-temperature and high-pressure (HTHP). The microstructures and surface morphologies of the metallic films are investigated by field-emission scanning electron microscope (FESEM) in this paper. It is shown that there are large numbers of small particles and a series of serrations on the inner surface of the films. It is calculated that the metallic film is mainly composed of (Fe, Ni) 3C, (Fe, Ni)2 3C6, but no diamond structure. The results by energy dispersive spectrometer (EDS) analysis are in good agreement with these by transmission electron microscopy (TEM). It can be concluded that the carbon atom groups coming from the decomposition of Fe-C compound rich in carbon in the film are deposited on the diamond surface directly and diamonds grow in the model of sandwich.