Abstract: ZL702A aluminum alloy after 490 ℃×4 h+500 ℃×6 h+520 ℃×8 h solution and quenching in the water medium at room temperature was aged at 160 ℃and 170 ℃for different time.The relationship between aging hardening behavior and precipitate transformation of ZL702A was studied by microhardness method and transmission electron microscopy (TEM).The results show that the aging hardening curves of ZL702A at both 160 ℃and 170 ℃exhibit double-hardness-peak aging behavior.The aging strengthening phenomenon is attributed to the combination of transformation of the GP zone to θ", θ', θ phases with coarsening of Q'phase.In the first hardness peak period corresponding to aging at 160℃for 12 h, the hardness of the alloy is 114 HV.At this time, the dislocation movement is severely hindered and the alloy obtains the most ideal aging strengthening effect.