After superplastic tensile deformation and triple heat treatment, the effects of triple heat treatment on superplastic tensile microstructure of TC21 titanium alloy were investigated. The results show that dynamic recrystallization occurred obviously in the process of TC21 titanium alloy superplastic deformation. The α phase content became more decrease with increase of deformation temperature and α?β phase transition start to happen. After superplastic deformation and β solid solution heat treatment for the first time, TC21 titanium alloy obtain single-phase β organizations. Through a high temperature aging and a low temperature aging in the (α β) phase region, fine acicular α phase precipitates out on β matrix, and TC21 alloy obtain baskets organizations. Acicular α phase content increases with the increase of deformation temperature and the second heat treatment temperature. With the increase of deformation temperature and the second temperature, acicular α phase content increases, and α grain grew up and intertwined which basketweave microstructure significantly.