Characterization of the bonding interfaces among particles of Al powder compacts prepared by pulse electric current sintering (PECS) process was investigated by means of scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The direct metal- to-metal bonding interfaces and the metal-to-oxide film layer-to-metal bonding interfaces were observed in Al powder compacts. The fraction of the direct metal-to-metal bonding interfaces in the powder compacts increased with increasing in sintering temperature or loading pressure. The oxide film covered at Al powder particles surface was broken and dispersed by plastic deformation of powder particles under loading pressure. Increasing in sintering temperature or loading pressure, the breakdown of oxide film was promoted.