A356.2（Sc，La） aluminum alloy was prepared by casting process. The refining effect of rare earth elements Sc and La on eutectic silicon and mechanical properties of aluminum alloy was tested and analyzed. The results show that the addition of rare earth element La alone can refine eutectic silicon in A356.2 （La） aluminum alloy to a certain extent， but has little effect on the improvement of mechanical properties. However， the eutectic silicon in A356.2 （Sc， La） aluminum alloy containing 0.38% Sc and 0.14% La has better refining effect and higher mechanical properties， The eutectic silicon is refined to 2.3 μ m. and the tensile strength and elongation reached 181.6 MPa and 4.0% respectively.The refining effect of rare earth Sc and La on eutectic silicon is mainly the result of both dispersion strengthening and fine grain strengthening， which are related to the precipitation of Al3Sc phase and rare earth La phase in aluminum alloy.