Abstract: The effects of the single pulse, the electromagnetic stirring and the electromagnetic stirring plus single pulse hybrid on the microstructures and properties of high strength Al-Cu alloy welds were investigated.The results show that the structures of weld with conventional MIG welding are coarse, oriented columnar grains;the ultimate tensile strength of welded joint is 286.5 MPa, ductibility is 2.4%;both the single pulse and the electromagnetic stirring can improve the mechanical properties by refining the microstructure;the electromagnetical stirring plus single pulse hybrid decreases the thermal gradient at the solid-liquid interface in the weld pool, enhances the density of heterogeneous nucleation, results in the coarse and oriented columnar grains reforming to fine equiaxed grains, and significantly improves the mechanical properties of weld joint, which the ultimate tensile strength is 326.0MPa and the ductibility is 7.8%.