Severe plastic deformation (SPD) techniques, such as equal channel angular pressing (ECAP), accumulative roll bonding (ARB) and high pressure torsion (HPT) have been extensively investigated to achieve. SPD techniques make use of plastic deformation process where no change in the cross-sectional dimension of a work piece occurs during straining. In this work, the effect of HPT on the aging behavior and microstructure in excess Mg-type Al-Mg-Si alloys including Cu are investigated. These alloys were investigated by hardness test and transmission electron microscopy (TEM) observation. The results show that processing by HPT leads to significant grain refinement with a grain size of 200-250nm.An age-hardening phenomenon is observed at 343K and 373K for the Al-Mg-Si alloys with HPT. Some precipitates were observed on grain boundaries.