Abstract: Homogenization treatment can eliminate alloy casting defects, improve composition segregation and enhance deformation ability.The effects of different homogenization time (2, 5, 10, 15, 20 h)and temperature (480, 500, 520 ℃)on the microstructure and mechanical properties of Mg-9Gd-3.5Y-2Zn-0.35Zr alloy were studied using optical microscope(OM), differential scanning calorimeter(DSC), X-ray diffraction(XRD), scanning electron microscopy(SEM), energy spectroscopy analysis(EDS)and universal tensile experimental machine and other means.The results show that the as-cast Mg-Gd-Y-Zn-Zr alloy mainly includes a block Mg₅ (Gd, Y, Zn)phase distributed in a network along the grain boundary and lamellar long-period stacking ordered (LPSO)phases, the coarse second phase easily cause local stress concentration and crack initiation, resulting in lower mechanical properties of the as-cast alloy.After homogenization treatment, large amounts of second phase are dissolved into the matrix, the mechanical properties ofthe alloyare significantlyimproved, the fracture mechanism also changes from a caststate brittle fracture to a plastic fracture, indicating that the material plasticity is significantly improved. The optimum homogenization process is 520 ℃/15 h, and the tensile strength, yield strength and elongation of the alloy are increased from 166.2 MPa, 130.2 MPa and 3.3%to 213.5 MPa, 154.5 MPa and 7.6%, respectively.