Abstract: The microstructure and mechanical properties of as welded and post weld heat-treated linear friction welded joints of TC17 titanium alloy were compared and analyzed. The results show that the microstructure of the welded joint is recovered and recrystallized. Due to the rapid cooling rate after welding, metastable β phase is formed, and the weld zone is softened; the microstructure in the thermo mechanical affected zone is elongated and refined along the stress deformation direction The microhardness of the heat affected zone decreases significantly because the secondary α phase is dissolved in metastable β phase. After post weld heat treatment, metastable β phase decomposes in aging and precipitates acicular secondary α phase with higher dispersion, which greatly improves the hardness of welding zone. The results show that due to the formation of metastable phase, the welded joints soften, and the tensile strength is 91.8% of the base metal strength, and the fracture is brittle fracture; the joints in the post weld heat treatment state have the effect of dispersion strengthening due to the precipitation of secondary α phase, and the tensile tests are all broken in the base metal, and the fracture is in the typical ductile fracture morphology.