The electron-beam welded microstructure of spray formed Al-Zn-Mg-Cu alloy was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy etc. The results indicate that the welds are composed of three zones, the base metal, nugget and heat affected zone. The width of the weld is 0.3~1 mm, and the weld nugget zone is composed of equiaxed grains with an average grain size of 3~8 μm, and the second phases are mainly distributed along the grain boundaries. Heat-affected zone is composed of α (Al) and Al/AlZnMgCu eutectic structure. Some of the heat affected zone have displayed remelting characteristics. After T6 treatment, most of the AlZnMgCu phases in weld nugget were dissolved into α (Al), and the eutectic structure in heat-affected zone disappeared