Abstract: Pure tungsten (PW), lanthanum-tungsten alloy (W-La17), and ternary composite tungsten alloy (W-X17) rods were prepared by cold isostatic pressing, intermediate frequency sintering, and swaging. The effect of rare earth oxide on the microstructure, second-phase distribution, and mechanical properties of the tungsten alloy rods was investigated, and the strengthening mechanism and fracture-toughness mechanism were analyzed and discussed. The results show that the addition of rare earth oxide effectively refines the grain size of tungsten matrix. Compared with pure tungsten electrodes, the sintered billets of the rare earth-doped tungsten electrodes exhibit one grade higher in granule size, while the swaged billets show one to two grades higher, indicating that doping by rare earth oxide effectively prevents the grain growth during sintering and swaging. After swaging deformation, the second-phase elements are uniformly dispersed in the tungsten matrix. Moreover, the addition of rare earth oxide contributes to Orowan strengthening in the tungsten matrix, leading to a certain degree of improvement in tensile strength and hardness of the tungsten electrodes. The lanthanum-tungsten alloys achieve the tensile strength of 1149 MPa, while the ternary tungsten alloys reach 1230 MPa, representing increases of 70.98% and 83.04%, respectively, compared to the pure tungsten rods. The hardness also increases from HV₃₀ 413 (pure tungsten) to HV₃₀ 425 (lanthanum-tungsten alloys) and HV₃₀ 431 (ternary tungsten alloys). The room-temperature tensile fracture of both pure tungsten and composite tungsten electrodes reveals the brittle fracture characteristics.