This study investigates the synthesis of single-phase nanocrystalline forsterite powder by mechanical activation with subsequent annealing. To produce forsterite powder, a mixture of talc and magnesium oxide powders was first milled by a planetary ball mill, and then annealed at 1000 and 1200°C for 1h. The synthesized powder was characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), scanning electron microscopy (SEM), and atomic absorption spectrometry (AAS). The initial temperature of forsterite crystallization was reduced to about 825°C after 20h of mechanical activation. The forsterite powder synthesized by 5h of mechanical activation with subsequent annealing at 1000°C for 1h had crystallites 40nm in size. The particle size of this sample was less than 500nm.