In the present work, Al-Mg-Zn alloys with compositions of Al- 2 at.% Zn — x at.% Mg, (x=1.8, 2, 2.4, 3 and 4.2) have been investigated. The developed precipitates and their growth have been followed as a function of aging temperature. The precipitates morphology was examined by scanning electron microscope (SEM) and correlated with the microhardness (HV) and differential scanning calorimetry (DSC) of the specimens. The structure of the precipitates has been detected by X-ray diffraction (XRD). Mostly, the precipitates are characterized as T′, T, η′ and η phases. The XRD charts analysis show that T′(Mg32 (Al, Zn)49) and T (Mg32 (Al, Zn)49) are cubic whereas η′ (MgZn2) and η (MgZn2) are hexagonal.η′ andrη phases have had a hexagonal structure of the same composition with slight different lattice parameters .