The microstructure of a ZL114A alloy and its mechanical properties were improved by the addition of the rareearth element Er. SEM, XRD, DSC and other material analysis methods were used to study the effects of different Ercontents on the microstructure and mechanical properties of the ZL114A aluminium alloy. The results show that grainrefinement can be achieved by adding suitable Er, the coarse dendrite structure in the alloy gradually tends to bespheroidized, the crystallization temperature of the primary α-Al phase and eutectic Si decreases, and the precipitated phaseAl3Er is enriched on eutectic Si, which plays a role in heterogeneous nucleation. With increasing Er content, eutectic Sievolves from slats to rods or near-spherical particles, and the mechanical properties of the alloy also improve. However,when the Er content exceeds a critical value (0.5 wt.%), the refining effect is not significant, and the mechanical propertiesdecrease. The alloy exhibits optimal performance when 0.5 wt.% Er is added, with the tensile strength and elongation rateincreasing by 11.43% and 52.8%, respectively.