The photovoltaic (PV) rapid growth suffers the severe shortage of silicon. The metallurgical route to solar grade (SoG) silicon is the alternative solution. One of the methods suggested the fractional melting process. Because the metal impurities in the metallurgical grade (MG) silicon such as Fe, Al, Ti and Cu deteriorate the efficiency of the solar cell seriously, it is important to remove those metal elements from MG-Si to upgrade the silicon. The refining behaviors of the metal impurities, however, do not equal in FM process. Cu and Al behaviors in the Si during FM process are studied using SEM, EPMA and ICP-AES. The diffusion coefficient and the grain boundary (GB) enrichment behaviors of the elements are rationalized to cause the difference. (C) 2010 Elsevier B.V. All rights reserved.