Abstract: The evolution law and mechanical properties of aging precipitated phase of Al12Zn2.4Mg1.1Cu alloy were studied by transmission electron microscopy, Vickers hardness tester and tensile tester equipped with in-situ heating holder,and the aging treatment process was determined. The results show that the main precipitated phase in the crystal is GPII after120 ℃/14 h aging. After the aging of 120 ℃/28 h, the main precipitate phase is η’ metastable phase and GPII region. Tensile experiments show that, the tensile strength of the test alloy is 749.6 MPa, and the yield strength is 688.5 MPa after aging at485 ℃/2 h solid solution+120 ℃/14h. In this state, the fracture mode of the alloy is transgranular+intergranular fracture.