Abstract: Aluminum alloy ingots with different contents of RE element were prepared, and then homogenization treatment following by thermomechanical treatment were carried out to study the effects of RE on microstructure, mechanical properties, electrical conductivity and thermal-resistance. At last, the acting mechanisms and existing forms of RE were analyzed. The results show that appropriate amounts of RE could refine the grains of as-cast alloy, but this had no influences upon the microstructure after thermo-mechanical treatment. RE could decrease the peak hardness and increase electrical conductivity, and the tensile properties decreased when the quality fraction of RE was more than 0.1%. The thermal-resistance of the alloys were improved by adding RE, and RE existed mainly in the form of β phase (AlCuREFeSi).