Abstract: Segmented carbon filaments were prepared by pyrolysis of acetylene using foam Ni as the catalyst. The effects of reaction conditions on the yield and the morphology of the product were studied . The growth mechanism of the sample is discussed. It is suggested that the different micro-crystal faces of the catalyst favor either the adsorption and dissociation of gaseous hydrocarbon or the carbon deposition respecctively. So the original shapes of the catalyst grains have affected the product morphology.