Abstract: The feasibility of using synergetic high-efficiency tandem PMIG welding of 60 mm thick 5A06 aluminum alloy plate was investigated and sound weld joints were obtained. The metallographic structure and mechanical properties of the weld joint has been analyzed. The results show that the base metal keeps its original fibrous structure along the rolling direction, and the microstructure of the weld is fine and homogeneous, which mainly consists of α(Al), β(Mg₂Al₃) and Mg₂Si. The average tensile strength and elongation of the weld joints is 306.17 MPa and 11.93%, which is 90.5% and 61.5% of the base metal, respectively. The contrast of the microstructure and mechanical properties of the samples consisting different layers of the weld joint indicate that,the welding heat input influences the microstructure and mechanical property of the weld joint. With the decrease of the welding heat input the HAZ becomes narrower, the mechanical properties are better. The sample which contains the front surface layer has the smallest HAZ width and the best mechanical properties due to its smallest welding heat input.