Abstract: According to the analysis of the thermophysical characteristics of several conventional titarcium alloys, friction stir weldability of titanium alloy had been discussed in this paper. According to the features of Ti alloy, the pin tool, welding anvil and protecting device were designed and applied for the friction stir welding of Ti alloy. By observation of the weld appearances and microstructures of the joint, as well as the mechanical property testing, the results showed that Ti-6Al-4V alloy can be successfully welded by FSW, and tensile strength of the joint can reach up to 90% of the base metal. With optimization of the welding parameter, procedure, pin tool profile and material, the property and performance of FSW of Ti alloy shall be unproved.