Abstract: K-TIG welding process test was carried out for 10 mm thick TC4 titanium alloy plate. The influence of welding current on the penetration depth and width was explored, the K-TIG single-pass welding penetration process was mastered, and the structure and properties of the welded joint were studied. The results show that the welding current has an impact on the penetration depth and width: when the current reaches 520 A, it is welded through, and when the current reaches 580 A, the TC4 plate is formed on both sides by single-sided welding. The joint structure is observed: the weld structure is sheet α phase, acicular martensitic α phase and residual β phase, the coarse-grained area of the heat-affected zone is equiaxed α phase and needle-like α phase, and the fine grain area is equiaxed α phase and flake α phase. The joint properties are studied: the hardness value of the upper part of the weld is lower than that of the middle and bottom, and the microhardness value of the lower and middle part of the joint is uniform. There is little difference in the hardness value of each zone, and the impact toughness and impact strength of the weld zone and the heat-affected zone are higher than those of the base metal.