The microstructures and corrosion behavior of AlSi5Cu 1Mg alloy modified with different contents of La were investigated.Optical microscopy observations showed that the microstructures of AlSi5Cu 1Mg-xLa (x =0,0.3,0.6,and 0.9 wt％) alloy transformed from coarse cellular to fine cellular as the content of La increased from 0 to 0.9 wt％.The results of electrochemical measurement and immersion test in 3.5 wt％ NaCl solution showed that the corrosion resistance of AlSi5Cu1Mg-xLa alloy strongly depended on its microstructures.The AlSi5Cu1Mg-0.6La sample exhibited the highest corrosion resistance due to its fine cellular structure and the cathode phases coated by the La element.The covering film of La hindered the corrosion electron flowing between the cathode and the anode.As a result,the corrosion current density of the AlSi5Cu1Mg-0.6La alloy was only about 40％ that of the matrix alloy in the electrochemical measurement.