Making use of graphite as electrode,we have prepared carbon nanotubes by the direct current arc-discharge method.The experimental results indicate that the carbon nanotubes are generated on the front-end surface and within the carbon accretion on the cathode.Using SEM adn TEM,we find no significant difference for the shapes and the structures of the generated carbon nanotubes when the pressure and the direct arc-current change.Under the pressure of hydrogen gas 11999Pa and direct arc-current 60A,we obtain a large number of straight and long carbon nanotubes with uniform calibers.