A combustion synthesis reaction has been developed for the α-Si3N4 powder under low nitrogen pressure. Si and solid state nitrogen source were used as the reactants, and ammonium halide powders were added as a catalytic agent. These powders were mixed and pressed into a cylindrical compact and wrapped up with an ignition agent (i.e., Ti + C). The synthesis reaction was triggered by combustion of the igniting agent. The product as synthesized is composed mostly of α-phase and in the form of agglomerated fine particles (0.1-1 μm in diameter). The effects of the additives and other experimental parameters on the process were investigated and a possible reaction mechanism was also proposed.