Abstract: The welding penetration and width of four types of Tungsten electrodes, W-La₂O₃, W-Y₂O₃, W-CeO₂ and W-ThO₂ (for reference) are measured and compared by means of DC TIG welding with stainless steel as the base metal. As it turns out that, there is no significant difference among the four types of electrods in terms of welding width, under the same experimental condition, and W-Y₂O₃ electrode exhibits the deepest welding penetration followed by W-CeO₂ and W-La₂O₃ as the medium and W-ThO₂ as the smallest. Studies indicate that the welding penetration has corresponding relationship with the electrode's hot emission ability, that is, the better the emission ablity, the deeper the welding penetration.