Mg15Al-xNd (x=0, 0.5, 1.0, 1.5, 2.0and 4.0wt.%) alloys were prepared by metal mould casting method and the microstructures and mechanical properties were investigated. The results demonstrate that primary α-Mg grain is significantly refined with the addition of Nd element in Mg15Al alloy, and the best refinement is reached at 1.0wt.%Nd content. Further increasing Nd content leads to the coarsening of primary α-Mg grains. The added Nd element is also the reason of the refined eutectic β-Mg17Al12 and increased dispersion. The β-Mg17Al12 phase is thoroughly changed from fibrous coupled eutectic into divorced eutectic when Nd content reaches 1.5wt.%. Al11Nd3 phase is formed when the addition of Nd reaches to 1.0wt.% and Al2Nd phase emerges in the microstructure with increasing Nd content up to 4.0wt%. Addition of Nd element significantly improves the mechanical properties of Mg15Al alloy at room temperature. The best tensile strength and elongation is achieved by adding 1.0wt% Nd into Mg15Al alloy.