Abstract: Carbon nanotubes were prepared by catalytic decomposition of CH4 or C3H6, and the effect of source gases on the yield and morphologies of the carbon nanotubes was investigated. When CH4 is used, besides a higher conversion, the resultant carbon nanotubes have a more regular and more homogenous morphology as evidenced by TEM. The XRD patterns of the products from both source gases are similar to that of graphite, but the degree of long-range order of these nanostructures is relatively low. Compared with the carbon nanotubes produced from C3H6, the carbon nanotubes produced from CH4 have a higher degree of long-range order, which suggests that CH4 is a more suitable source gas to produce carbon nanotubes. The Raman spectrum indicates that there are more defects in the structure of carbon nanotubes produced from C3H6 than from CH4.