Abstract: The effect of vanadium on the microstructure and mechanical properties of 316L/T91 tungsten inert gas（TIG）welding joints fabricated by four welding wires with the vanadium contents of 0, 0.2%, 0.4% and 0.6% was investigated. The results show that the weld microstructure of the four welding wires is composed of austenite and δ ferrite. With the increase of the vanadium content in the welding wire, the microstructure of the welded joint becomes more fine and uniform;the tensile strength is improved, the impact absorption energy does not change much. It can be seen from the impact fracture that the dimple size increases to some extent with the increase of the vanadium content, indicating that vanadium has a certain improvement effect on impact toughness, but the effect is limited. The microhardness near the fusion line on the T91 side is significantly higher than that of other regions without vanadium, and there is a large fluctuation. After adding vanadium, the hardness in this region decreases.