The major problem in aluminum industry is a die soldering resulted from chemical and mechanical reactions of mold and molten aluminum in die casting process. The reactions lead to the formation of intermetallic compounds such as Al-Fe and Al-Fe-Si phases when the molten aluminum contains Si. This diffusion reaction causes die erosion and forms a soldering layer on the aluminum casting products leading to bad die accuracy and the quality of aluminum products. In this study, Fe and Si contents were varied simultaneously with reaction time. First of all, ceramic molds were made to fix a die steel. Then Al melts which are pure Al, 0.5Si-0Fe, 2.5Si-0Fe, 0Si-1Fe, 0.5Si-1Fe, 2.5Si-1Fe were poured into the ceramic molds at 730 ℃. After that, the samples were reacted in a holding furnace for 15, 30, 60 min and air cooled. The thickness of die erosion and soldering layer could be checked and identified.