Abstract: 0.8 mm thick TNW700 titanium Alloy sheets were welded by the TIG welding. Microstructure，mechanical properties and hardness distribution were studied. The results show that the TIG welded joint of TNW700 sheets possesses excellent performance. The weld zone is mainly composed of acicular martensite α' phases, HAZ is mainly composed of α phases and β phases in small quantities and the microstructure in HAZ is asymmetrical. The strength of the welded joint is higher than that of the parent metal by about 15%, the elongation is about 54% of that of the parent metal. There was the highest microhardness in HAZ, and the microhardness of weld zone is higher than that of base material. There was obvious hardening tendency in HAZ.