A large quantity of loosely-entangled carbon nanotubes was prepared by arc-discharge method. Samples containing the nanotubes were oxidized at high temperature. The tubes can remain after a relatively long time(over 1h) and high temperature (of 850 °C oxidization. The amounts of the defect and other structure imperfects might be substantially minimized in the loosely-entangled nanotubes, so the stability of the tubes was greatly improved and the nanotube could have much more opportunities to survive during oxidization. This is consistent with Raman scattering results.