Abstract: The effects of solution treatment (T4 treatment)on the microstructure evolution and mechanical properties of Mg-3Zn-1Y-1.5Nd-0.4Zr alloy were investigated systematically.The microstructure of as-cast and T4 Mg-3Zn-1Y-1.5Nd-0.4Zr alloy was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy(EDS). The mechanical properties of as-cast and T4 Mg-3Zn-1Y-1.5Nd-0.4Zr alloy were tested by uniaxial tensile test and microhardness test.The results show that the continuous second phase at the crystal boundary of the cast Mg-3Zn-1Y-1.5Nd-0.4Zr alloy breaks and globalizes during solid dissolution.The comprehensive mechanical properties of T4 Mg-3Zn-1Y-1.5Nd-0.4Zr alloys increase first and then decrease.The ultimate tensile strength, yield strength and elongation of Mg-3Zn-1Y-1.5Nd-0.4Zr alloy are 278.20 MPa, 226.79 MPa and 13.53%, respectively, when it is held at 490 ℃for 26 h. During solution treatment, spheroidization occurs in the second phase of Mg-3Zn-1Y-1.5Nd-0.4Zr alloys and the dissolution of solute elements in the second phase produces solid dissolution reinforcement, which improves the comprehensive mechanical properties of the solid-soluble Mg-3Zn-1Y-1.5Nd-0.4Zr alloy.