Abstract: The effect of rare earth Y on the microstructure and tensile properties of A356 alloy was studied by using OM,SEM and tensile testing machine.The results indicate that rare earth Y is an excellent modifier for A356 alloy.Y could not only refine primary α-Al phase,make the grain fine and equiaxed,reduce secondary dendrite arm spacing,but also could result in the transformation from striation texture to fibrous eutectic Si.When 0.4wt% Y was added,the values of the tensile strength σb and elongation δ of A356 alloy reached 298 MPa and 9.5%,which were increased by 29.6% and 21.5% respectively,compared with the alloy without adding Y element.