Abstract: Single-side friction stir butt welding tests for automotive titanium alloy Ti-6Al-4V-0.2Y plate with thickness of 6 mm were conducted,and the macroscopic morphology,X-ray nondestructive flaw detection,microstructure,surface hardness and mechanical properties of the joints were tested and analyzed in this paper.The results show that the joints have good shapes,bright surfaces,favorable mechanical properties and no obvious defects;tensile strength of the joint at room temperature reaches 900 MPa and the joint coefficient is up to 96%;the area with maximum and minimum hardness of weld joint is located in the weld nugget zone and the heat-affected zone of forward side,respectively.