The pure Mg2Ni intermetallic was synthesized by self-propagating combustion mode and thermal explosion mode respectively. And the reaction process of thermal explosion was researched under different preheat temperatures. The results show that solid combustion exists at lower temperatures, and the degree of reaction increase with the decrease of preheat rate. A further experiment of Combustion Front Quenching (CFQ) was carried out successfully in cylindrical steel mould by adding some Al-Ti-C powder that is accepted as a high exothermic system on the top of Mg-Ni samples. The physical and chemical changes of all region in the quenched samples during the combustion synthesis were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and x-ray diffraction (XRD). The results show that the Mg2Ni is directly synthesized rather than through other intermediates and the synthesis process of Mg2Ni can be express as: (1) solid combustion in the pre-combustion stage; (2) liquid combustion in the combustion process; (3) nucleation and crystallization of the product after the reaction; (4) uniformizing of the composition in the heat preservation stage.