The microstructure and mechanical properties of as-cast EV31A alloys are investigated by using optical microscope （OM）， X-ray diffractometer （XRD）， scanning electron microscope （SEM）， energy dispersive spectrometer （EDS）， transmission electron microscope （TEM）， and electronic universal testing machine. Experimental results show that the microstructure of as-cast EV31A alloys is the α-Mg matrix and Mg₄₁（Nd_0.9Gd_0.1）₅ eutectic phase. Due to the low content of rare earth elements， the eutectic reaction occurs in the late stage of α-Mg crystallization， manifested as the Mg₄₁（Nd_0.9Gd_0.1）₅ phase containing rare earth elements mainly distributed at the grain boundaries of α-Mg， except for a small amount of solid solution in the α-Mg matrix. The Mg₄₁（Nd_0.9Gd_0.1）₅ phase has a bcc structure with a lattice constant of 0.285 nm. The grain size of α-Mg in the alloy is 56.8 μm. The ultimate tensile strength， yield strength and elongation are 207 MPa， 124 MPa and 7.0%， respectively. The excellent mechanical properties of alloys are mainly attributed to the fine grain strengthening brought by Zr，solid solution strengthening of solute atoms such as Gd， Nd， Zr， etc， and the synergistic effect of multiple strengthening methods such as second phase strengthening brought by eutectic Mg₄₁ （Nd_0.9， Gd_0.1）₅ phase.