Combustion synthesis (CS) of alpha-silicon nitride (Si3N4) powders was accomplished at a nitrogen pressure lower than 3 MPa. The combination of mechanical activation and chemical stimulation was effective in enhancing the reactivity of Si powder reactants, which was responsible for the reduction of the minimum nitrogen pressure normally required for the CS Of Si3N4. This breakthrough indicates that nitriding combustion of silicon in pressurized nitrogen could be promoted by activating the solid reactants instead of by increasing the nitrogen pressure. The phase content Of alpha-Si3N4 in the as-synthesized product is over 90 wt%. Scanning electronic microscopy observation showed that the combustion-synthesized Si3N4 powders are submicron-sized particles with spherical morphologies.