Rectangular Co3O4 nanosheets with the thickness of about 50-100nm were fabricated by calcining the isomorphological CO(CO3)(0.35)Cl-0.20(OH)(1.10) precursor, which were produced via the reaction Of CoCl2 and CO(NH2)(2) in the presence of PEG (polyethylene glycol)-10000. Thus-prepared Co3O4 sheets exhibited high efficiency for the growth of carbon nanotubes in pyrolyzing ethanol.