Abstract: Hydriding combustion synthesis of Mg₂NiH₄ was conducted at different heat treatment regime and hydrogen pressures in self-developed reaction apparatus. The relationships among the purity, hydrogen pressure, synthesis temperature and holding time at hydrogenation and at maximum temperature were mainly studied. Pure Mg₂NiH₄ is obtained in the initial pressure of 1.5MPa, holding 120min at synthesis temperature of 808K and 60min at Mg₂Ni hydriding temperature of 653K or holding 60min at synthesis temperature of 850K and 90min at 653K. The results indicate that a mechanism of liquidtrigger, liquid-solid and solid-solid diffusion reaction between magnesium and nickel plays an important role in the combustion synthesis of Mg₂Ni.