NiB powder was prepared by mechanically alloying in this paper and was composited mechanically with MgNi amorphous alloy. The effect of NiB on structure and electrochemical performance of MgNi-electrode was studied. The XRD analysis show that MgNi-NiB composite is amorphous phase. The electrochemical characteristics of this composite were also studied. The cycle life of the MgNi-NiB electrode is improved.