Abstract: The relationship between mechanical properties and weld appearance of the joints by the two-pass welding with large current(DL) and the four-pass welding with small current(XS) were in-vestigated in tandem GMAW of 20mm thick 2519 aluminum alloy plate. The results show the tensile strength of both joints are less than 60% of that of the base metals, and the tensile strength and elongation percentage of the DL joints are larger than those of the XS joints, but the impact toughness of the DL joints is smaller.Based on the merits of the above two process, a new process named fourpass welding with large current(DS) was puts forward. The experimental results show the tensile strength of the DS joint is up to 296.4 MPa, equivalent to 61.2% of that of base metal and the impact toughness of the DS joint improved simultaneously.The DS weld zone is composed of αphase and eutectic structure grains. Hardness of the weld is the lowest on the whole weldment, and the hardness of the HAZ is higher because the θ phase dissolve and separate out renewedly.