The EXAFS technique was used to study the changes of Fe and Cu atom neighbor environment following the milling time and composition of Fe-Cu system. The resutls show that the range of Fe-Cu solid solution can be greatly extended and can form nanometer sized non-equilibrium metastable alloy particles mechanical alloying. For Ｆｅ80Ｃｕ20(160h), K-edge absorption curve and radial structure function of Cu are similar to that of a-Fe powder, has the bcc structural characte-ristics, the Fe-Cu alloy particles is bcc structure also. The structure of Fe-Cu alloy in Ｆｅ60Ｃｕ40(160h) is the fcc structure, it is different from that of Ｆｅ80Ｃｕ20(160h). In nanometer sized Fe-Cu metastable alloy particles of Ｆｅ60Ｃｕ40(160h), Cu and Fe are not uniformly dispersed, Cu is a little richer in the core, but Fe is abundant on the surface.