Abstract: Nonhomogeneous diffusion thought to eliminate the embrittlement of steel-Al-20Sn interface was presented and realized by conducting steel-mushy Al-20Sn rolling casting bonding. The interfacial structure changed and the interfacial embrittlement was eliminated. The results showed that under the condition of 500℃ steel plate preheat temperature and 10mm/s rolling casting speed, when solid fraction was 34.3%, the interface was made up with the right Fe-Al compound and solid solution alternatively, and because of the elimination of interfacial embrittlement, the maximum interfacial shear strength was 69.9MPa.