Abstract: The laser self-fusion welding test was carried out for 10 mm thick Ti6321 alloy, and the microstructure and properies of the obtained joint were tested and analyzed. The results show that the microstructure of the weld zone is mainly a "basket" structure formed by thick β cylindrical grain and fine needle-like martensitic α’ phase. The middle of the weld is largeα equiaxed grains, the interior of the grain is mainly composed of the needle-like martensite α’ phase, α phase and α+β phase.The microstructure of the heat affected zone is unevenly distributed, and the microstructrue near the weld seam is mainly basket structure formed by α+α’ phase, the microstructrue near the base material is mainly composed of the bulk α phase and the original（α+β） phase, and the microstructrue of the transition zone is mainly α phase transformed from β phase, a small amount of needle α’ phase and residual β phase. The joint is broken at the base material during tensile test, the cold bending performance of the welded joint is qualified, and the impact toughness is reduced compared to that of the base material.