Abstract: Key hole TIG welding experiments of 16 mm and 30 mm thick TA2 plate were conducted respectively.The influence of welding parameters on the weld appearance, inner quality, microstructure and mechanical properties of the welded joints was investigated.It has been verified that one side welding both sides formation of 16mm thick TA2 plate without bevel preparation can be successfully obtained by using optimized welding parameters.High welding current causes coarse grains and slightly increase of hardness in the weld.For 30 mm thick Y-groove plate,14mm and 10mm blunt edge penetration with good weld appearance and inner quality can be achieved by using key hole TIG welding from back side and front side respectively, and conventional TIG welding can be used for filling and covering directly.The strength of TA2 plate joints made by single key hole TIG or combined with conventional TIG is equivalent to that of the base metal, and the mechanical properties are good.