The Mg-based hydrogen storage alloy Mg2-xAlxNi(x=0.1-0.5) was synthesized by combustion synthesis. XRD indicates that a new phase with the cubic Ti2Ni structure appears in the product, and SEM shows that there are a large number of defects on the alloy surface. The effect of partial substitution of Al for Mg on the electrochemical performances of Mg2Ni was investigated. The results show that Al addition affects its electrode characteristics strongly. The electrochemical capacity and cycle lives of Al-containing alloys increase strongly compared to the Al-free alloy. This is attributed to the structure of a new phase (Mg3AlNi2), and the formation of the protect layer of Al2O3. In addition, the results reveal that mechanical grinding is beneficial to improve activation behavior and the maximum electrode capacity, but can not improve the cyclic stability due to breaking of Al2O3 protect layer.