Abstract: The electron beam welding tests of 24 mm thick 2A14-T6 aluminum alloy plate were carried out, and the best welding process parameters were obtained. The results show that the joint deformation is small, the depth-width ratio is large,and the flaw detection result is Grade I. The microstructure of each micro-area of the joint is different. The center of the weld is dendrite, the microstructure of the weld near the fusion line is columnar grains, the heat-affected zone is coarsened oblate fibrous structure, the precipitation strengthening phase particles increase, and the microstructure of the over-aging zone is similar to that of the base metal, which is oblate fibrous structure. There is a small amount of precipitation strengthening phases in the grain of the weld zone, and there are eutectic phases formed by copper, silicon and other elements and the matrix phase at the grain boundary, which are distributed in network shape. There are fine Al₂Cu precipitation strengthening phase and massive eutectic phase distributed in strip shape in the base metal zone. The microhardness of the weld zone is the lowest,that of the heat-affected zone rises first and then decreases with the increase of the distance form the weld center, and that of the base metal zone is the highest. The average tensile strength and elongation after fracture of the joint are 387.7 MPa and 3.4%respectively. There are tearing edges and a small number of large and shallow dimples on the micro-fracture, which is a brittle-ductile mixed fracture mainly characterized by brittleness.