Abstract: Modified phenolic resins were obtained by doping with cobalt oxide sol using ethanol as medium, and then treated in coke bed after hardening under the condition of buried carbon. The structure of pyrolytic carbon was studied by means of scanning electron microscopy (SEM), highresolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Results showed that cobalt oxide sol was dispersed homogeneously in phenolic resins, the transition metal was produced in situ and then acted as a catalyst in pyrolysis process of phenolic resins, converting amorphous carbon into graphite structure. The scanning electronic microscope and the transmission electron microscope images of pyrolytic carbon showed that there were massive carbon nanotube structures formed in the pores of pyrolytic carbon. The content and appearance of the carbon nano-tubes varied with the content of cobalt oxide sol.