Abstract Mo–Si powders were milled using an attritor mill with a rotation speed of 300 rpm and ball to powder mass ratio of 24:1. X-ray diffractometry (XRD) and transmission electron microscopy (TEM) were used to investigate phase transformation, microstructure, elemental constituents and morphology of the as-milled powders. Thermodynamics analysis was carried out using Miedema model. The results show that the structure evolution of Mo–Si binary system follows: dispersion of Si in Mo → solid solution in Si boundary → α-MoSi 2 and β-MoSi 2. There is thermodynamics driving force for Mo–Si binary to form solid solution and amorphous phase. Mo–Si binary system forms solid solution in the boundary system of Si. Si grain is further refined by the formation and detachment of MoSi 2 from the Si boundary, which leads to the disappearance of Si reflections in XRD patterns.