| There always exist a molten film surrounding diamond single crystal in the course of diamond growth at high temperature and high pressure (HPHT) by using the technique that graphite discs are placed alternatively with catalyst discs or mixture which are mixed by catalyst powder and carbon powder are molded into columns in cylinders, its thickness remains to between less to 100 μm and several hundreds. It is undoubtedly that graphite diffuses across the film towards growing diamond, and its structure is broken and makes a transition to diamond under the effect of the film. Therefore, the film plays an important role in the diamond growth at HPHT.In present paper, in order to simulate the effect of molten metallic film we used electroplated diamond with nickel film as seed and the thickness of film is nearly same to molten metallic film. The electroplated diamond seeds were placed in holes made in the carbon discs regularly, said holes being made at a substantially equal distance. Moreover, the effect to diamond in synthesis caused by different thickness of film was studied.The morphologies and compositions of nickel film were systematically investigated using scanning electron microscope and X-ray diffraction methods before and after synthesis. It was shown the transition from graphite to diamond was accomplished in the nickel film and then precipitated on the seed, but not the carbon with diamond structure recombined on the surface of diamond. We observed morphologies that on the nickel film was similar to those of corresponding diamond surface presented cellular particles.The synthetical results from diamond seed with 60 mesh which electroplated nickel film from 90 μm to 130μm was well. The cell assembly was brought up to a pressure 5.5～6.0GPa by high pressure apparatus and heated to a temperature of approximately 1700～1750K in 12～14 minutes. The grown diamond with cube-octahedral and octahedron shape, grain size was 0.7mm...
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