A mechanical alloying process was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and magnetic measurements for 6.5 wt% Si-Fe powders. The alloying process was divided into three stages. In the first stage (< 11 ks of the milling time), the Curie temperature, T(C), was the same as that of pure Fe, which indicated that the particles were not yet alloyed. At a milling time of 22 ks, the second stage, a large calorific value and a large coercive force, H(C), were observed and T(C) was not clearly observed, which indicated that the particles had a precise lamellar structure and had a large internal stress. In the third stage (> 90 ks), the calorific value and H(C) decreased. At the same time, a unique, and smaller T(C) was observed, which indicated that the uniformity of the powders increased.