One of the major issues in fabricating the Al alloy composites reinforced with SiC particulates is to avoid interfacial reaction products, i.e., Al₄C₃ and Si The formation of such interfacial reaction products can be supressed by the presence of adequate amount of Si within the matrix of the composite. According to the calculations, Si contents required to prevent the interfacial reactions in the SiC/Al composite were found to increase with increasing temperature. In addition, there exists a transient temperature near 620℃, at which a sudden increase in the equilibrium Si contents is required to prevent the formation of Al₄C₃. Experimental method to verify the theoretical results is also demonstrated.