Abstract: Al CoCrFeNi_2.1 eutectic high-entropy alloy is an alloy with good toughness and high temperature properties. In order to investigate the potential of electron beam welding in the field of the alloy, the effect of the variation of electron beam current on the morphology of the joint with the thickness of 3.5 mm was studied, the microstructure and mechanical properties of the welded joint were analyzed, and the optimal electron beam welding process parameters were obtained. The results show that compared with the base material（BM）, the weld zone（WZ） has finer lamellar microstructure, but the structure has a certain orientation. The hardness is also increased compared to that of the BM due to the weakened elemental enrichment of WZ and the reduction of grain size. The tensile strength and elongation of the welded joint are 873 MPa and 21.8%,respectively. The fracture occurs at the fusion line, and the softening problem occurs at the position.