A large amount of carbon nanotubes with uniform diameter were produced from catalytic decomposition of C2H2 or CH4 over perovskite oxide LaCoO3 catalyst precersor. The result of XRD measurement indicated that after reduction of LaCoO3 at 700 degreesC cobalt existed chiefly as Co-0 particles supported and separated by La2O3. La2O3 can prevent Co-0 from agglomeration. The size of Co-0 nanoparticles determined the diameter of carbon nanotubes. The morphologies and microscopic structure of carbon nanotubes were examined by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman. Reduction of LaCoO3 in H-2 and thermal oxidation of carbon nanotubes in air were made by thermogravimetric experiments (TG). XPS and Raman results revealed that the carbon nanotubes made from CH4 are probably more graphitized than those made from C2H2.