Abstract: Different amounts of Ce-La complex rare earths were added to Al-Si-Cu-Mg-Ni alloys. The effects of different Ce-La composite rare earth additions on the microstructure and mechanical properties of as-cast Al-Si-Cu-Mg-Ni alloy were investigated by microstructure observation and mechanical properties test. The results show that a large number of massive primary Si phase and acicular eutectic Si phase exist in Al-Si-Cu-Mg-Ni alloy without rare earth. The primary Si phase diameter and eutectic Si phase size decrease first and then increase with the increase of Ce-La composite rare earth content. The primary Si phase diameter and eutectic Si phase size of the alloy are the smallest when Ce-La rare earth content is 0.4wt%. With the increase of Ce-La, the tensile strength and elongation of Al-Si-Cu-Mg-Ni alloy firstly increase and then decrease. When the Ce-La composite rare earth content is 0.4wt%, the tensile strength and elongation of Al-Si-Cu-Mg-Ni alloy reach the maximum value, which are 296.5 MPa and 2.9% respectively.