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The influences of the two-step aging time on mechanical properties and microstructure of 7XXX aluminum alloy were studied by the experiments of normal temperature tensile, electrical conductivity, optical microscopy (OM), scanning electron microscopy (SEM) and inter-granular corrosion. The results show that after the two-step solid solution and two-step aging on 7XXX aluminum，its yield strength, hardness and electrical conductivity increase with the increase of aging time，and the tensile strength changes little while the rupture extension decreases with the increase of aging time. The yield strength, hardness， electrical conductivity, tensile strength, and rupture extension reach 661 MPa，70 HRB，34.68% IACS， 684 MPa，13.67% respectively when two-step aging is at 165 ℃ for 16 h. The undissolved second phases and impurity phase are found in alloy by metallograph，which are confirmed as Al7Cu2Fe and impurity phase containing Si by EDS. The intergranular corrosion depth reaches the maximum 23.34 μm, and the grade of intergranular corrosion resistance improves from the third grade to the second grade after two-step aging at 165 ℃ for 16 h.
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