The amorphous Mg–Al–Ni composites were prepared by mechanical ball-milling of Mg 17 Al 12 with x wt.% Ni (x=0, 50, 100, 150, 200). The effects of Ni addition and ball-milling parameters on the electrochemical hydrogen storage properties and microstructures of the prepared composites have been investigated systematically. For the Mg 17 Al 12 ball-milled without Ni powder, its particle size decreases but the crystal structure does not change even the ball-milling time extending to 120h, and its discharge capacity is less than 15mAhg −1 . The Ni addition is advantageous for the formation of Mg–Al–Ni amorphous structure and for the improvement of the electrochemical characteristics of the composites. With the Ni content x increasing, the composites exhibit higher degree of amorphorization. Moreover, the discharge capacity of the composite increases from 41.3mAhg −1 (x=50) to 658.2mAhg −1 (x=200) gradually, and the exchange current density I 0 increases from 67.1mAg −1 (x=50) to 263.8mAg −1 (x=200), which is consistent with the variation of high-rate dischargeability (HRD). The ball-milled Mg 17 Al 12 +200wt.% Ni composite has the highest cycling discharge capacity in the first 50 cycles.