Molecular dynamics simulations have been used to study the three kinds of multi-wall nanotube oscillators. The results show that the shorter the inner tube of the oscillators，the larger the oscillation frequency，and the fluctuations ofthe axial force acted on the inter tube are also larger. The inner tube rotatesabout the tube axis while oscillating along the tube axis. The rotational kinetic energy is fluctuating and closely related to the length of the inner tube. The study results can be used in developing new technology of producing carbon nanotubes.