Abstract: Under the condition of adding TA1 pure titanium middle layer filling plate, hidden arc welding test was carried out on TA15 titanium alloy plates with thickness of 64 mm, the microstructure, tensile properties of welded joint and hydrogen, oxygen, nitrogen content in weld seam were analyzed; Tensile properties of the welded joint adding interlayer were compared with that of the ordinary hidden arc welded joint without interlayer. Results show that the microstructure of the weld seam zone of welded joint adding interlayer was larger size of columnar crystal, intracrystalline acicular α′ phase distributed in different directions, the primary α phase and a small amount of β phase tissue were in the base metal area, α phase and α′ phase were found in heat affected zone. After adding middle layer, the tensile strength of the welded joint was lower than ordinary hidden arc welded joints, but its plastic increased significantly, the contents of hydrogen, oxygen and nitrogen in the welded joint were lower than those in the base metal.