Carbon/carbon core/shell nanofibers with length up to several micrometres have been prepared by co-pyrolysis of tetrahydrofuran and ferrocene in a stainless steel autoclave at 600 °C. The diameter of carbon core is ~10 nm, and the thickness of carbon shell is ~20 nm. It is found that the graphene layers of carbon core are perpendicular to the ones of carbon shell in stacking orientation. Comparative experiments confirm that the metallic iron catalysts, originating from the decomposition of ferrocene, are responsible for the formation of nanofibers. When the ferrocene is absence, only solid carbon spheres are observed. Moreover, hollow hexapod-like carbon materials can be obtained with water introduced into reaction system.