The effects of the NiB doping on the structure and electrochemical characteristics of the MgNi hydrogen storage alloy were investigated systematically. NiB was prepared by mechanical alloying (MA). XRD pattern shows the main phase of NiB alloy consists of Ni4B3, Ni3B and Ni2B. MgNi-NiB composite was also prepared by MA. XRD pattern shows MgNi-NiB composite alloy has amorphous structure and SEM photographs suggest a particle size of about 2-3 mu m in diameter. Compared with MgNi alloy, MgNi-NiB exhibits better cycle stability. After 50 charge-discharge cycles, the discharge capacity of the MgNi-NiB composite was 39.29% higher than that of MgNi alloy. The discharge capacity of the 100th cycle was 40.66% of the initiate and 93.24% of the 30th cycle discharge capacity. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and anticorruption test (potentiodynamic polarization) were also carried out. The results show that the cycle stability and the anti-corrosion behavior of MgNi alloy in alkaline solution were improved by NiB doping. (C) 2007 Published by Elsevier Ltd on behalf of the International Association for Hydrogen Energy.