Abstract: The metallurgical structures,mechanical properties and fractographs of electron beam welded 5383 aluminum alloy joint were studied by means of metallography observing,mechanical test and SEM technology. The results showed that the tensile strength of the joint was lower than that of base metal. The fractographs of the tensile specimens had dimple surfaces. The crystallizing morphology on the weld metal zone was equiaxed the strengthening phase evenly distributed in the substrate,and that on the fusion area were columnar dendrites. Due to the primary dendrite around the bond line affected by the temperature gradient in the solidification process,columnar dendrit perpendicular to the bond line featured the microstructure near the bond line. Scanning function was tried to eliminate porosity deflect,which had a high chance to form in the root of the weld,but scanning function alone couldn't eliminate the deflect completely.