In this work, a new method for the preparation of magnesium silicon nitride (MgSiN2) nanopowder was studied using a two-step process in nitrogen gas from Mg/Si starting mixtures. This method is known as mechanical alloying followed by heat treatment. The results showed that the compositions of the combustion products depended on the starting mixtures. In addition, the content of magnesium and silicon in the starting powder should fulfil the condition Mg/Si = 2 to obtain single phase MgSiN2.Single phase MgSiN2 nanopowder can be fabricated from Mg and Si powders with mole ratio of 2:1 at 1350°C in N2 atmosphere. Composition and structure of reactants and products were examined by X-ray diffraction, field emission scanning electron microscopy and high resolution transmission electron microscopy.