Abstract: The welding experiment of 6 mm thick 5083-H111 aluminum alloy hot rolled plate was carried out by metal inert gas welding. The variation of macro morphology and mechanical properties of joints with different process parameters was studied, and the effect of microstructure and element distribution in different regions on mechanical properties of the joint was analyzed. The results showed that the surface of all joints with optimized process parameters had no obvious defects. The weld width increased with the increase of wire feeding speed. Complete recrystallization occurred in heat-affected zone near the fusion line, and coarse equiaxed crystals were formed. The edge of the weld formed columnar crystals along the heat dissipation direction, and the fine equiaxed crystals were found in the center of the weld. Fe and Mn were seriously segregated in the heat-affected zone, forming Al6(Fe, Mn) phase. Mg is mainly distributed in the grain boundary of the weld and formed β(Al3Mg2) phase. The tensile test results showed that the maximum tensile strength of the joint could reach 307 MPa, which was about 96% of the base metal, and the fracture occurred in heat-affected zone with ductile fracture. Affected by the welding heat input, the hardness of the weld and heat-affected zone were lower than that of the base metal. With the increase of welding heat input, the hardness of the weld and heat-affected zone decreased.Highlights: (1) The joints with good formation were obtained by optimizing the welding process parameters.(2) The effect of welding parameters on the macro morphology and pore distribution of joints was studied.(3) The effect of microstructure and element distribution in different regions on mechanical properties of the joint was clarified.