Solid-state processing via the bulk mechanical alloying enables us to directly fabricate Mg2X semi-conductive material performs. Precise control of chemical composition leads to investigation on the dilution and enrichment of X in Mg2X. Two types of solid-state reactivity are introduced: e.g. synthesis of Mg2Si from elemental mixture Mg – Si is nucleation-controlled process while synthesis of Mg2Sn from Mg – Sn, diffusion-controlled process. Thermoelectricity of these Mg2X is evaluated for discussion on the validity and effectiveness of this new PM route as a reliable tool for fabrication of thermoelectric compounds.