Abstract: To address the issues of low mechanical properties and poor corrosion resistance in molybdenum welded joints, this study investigated the effects of adding Re foils with different thicknesses to the weld metal during electron beam welding. The aim is to explore the mechanisms by which varying Re content influences the microstructure and properties of Mo welded joints. Results show that the addition of Re refines the grain structure in the weld zone and forms a solid solution. As the thickness of the Re foil increases, the tensile strength of the joints gradually improves. When the thickness of the added Re foil is 0. 1 mm and 0. 2 mm, the improvement in the mechanical properties of the welded joints is not significant, and fracture still occurs in the weld zone. However, when the thickness of the Re foil is increased to 0. 3 mm, the weakest part of the welded joint shifts from the weld zone to the heat-affected zone. With a Re foil thickness of 0. 5 mm, the joint strength reaches 364. 67 MPa, representing a increase of 319% in tensile strength. The corrosion current density of pure Mo welded joints is 4. 108 × 10^-7 A/cm², while that of the joints with added Re foil is 5. 029 × 10^-8 A/cm², indicating a reduction in corrosion current density. The addition of Re enhances the mechanical properties and corrosion resistance of the Mo joints through the synergistic effects of solid solution strengthening and grain refinement.