Experiments have been carried out to investigate the damping behaviors of commercially pure aluminum (L2) prepared by equal-channel angular pressing (ECAP). The damping characterization was conducted on a DMTA-V apparatus. The internal friction was measured at frequencies of 0.1, 0.3, 1.0, 4.0 and 8.0 Hz over the temperature range of 20~150°C. The measured damping capacity shows that ultra-fine grained structure pure Al (L2) prepared by ECAP has a damping capacity that is enhanced in comparison with coarse one, especially when the temperature is higher than 60°C. The dependence of the damping capacity at room temperature on the strain amplitude shows a nonlinear characteristic, and increases rapidly with the strain amplitude (0) when 0 is comparatively low. While the strain amplitude is higher than certain value, the damping capacity will become saturated slowly. The high damping capacity of the pure Al prepared by ECAP was attributed to the high density of dislocations and ultra-fine grained structure.