Abstract: This paper adopts the electron beam weld (EBW) to weld Ti17 alloy, and makes testing on the mechanical properties of its weldments by means of tension testing at room temperature and 400℃, then analyses the microstructure of Ti17 alloy EB weldments by optical micrographs. It is found that tensile strength is not lower but higher than those of base metal. The Ti17 alloy welding joint have a thicker skin than its matrix on gap. The hardness of weld metal and HAZ are also higher than that of base metal. The microstructure of base metal and HAZ is like network made up of α+β. The microstructure of weld metal is threadlike α on the base of β, and the grains have grown thinner. All these prove that ideal welded joint of Ti17 alloy can be acquired by the way of EBW.