The fine-grained microstructure of TA15 titanium alloy was prepared through two-step forging technology combined with high and low temperatures, and a transnormal superplastic elongation of more than 2000% was obtained. The superplastic behaviour and microstructure evolution were systematically researched at different temperatures and strain rates through superplastic tensile test. The results indicate that the fine-grained TA15 alloy exhibits superplasticity at temperatures of 760-980°C and initial strain rates from 1.1 × 10-2 to 5.5 × 10-5 s-1. The optimal superplastic conditions are 940°C and 3.3 × 10-4 s-1, in which the average elongation is 2526% and the maximum elongation is 2743%. During superplastic deformation, dynamic recovery and recrystallization occur obviously, and the corporate effect of strain hardening and recrystallization softening decides the superplastic ability directly. The fine-grained microstructure of TA15 titanium alloy was prepared through two-step forging technology combined with high and low temperatures, and a transnormal superplastic elongation of more than 2000% was obtained. The superplastic behavior and microstructure evolution were systematically researched at different temperatures and The results indicate that the fine-grained TA15 alloy exhibits superplasticity at temperatures of 760-980 ° C and the initial strain rates from 1.1 × 10-2 to 5.5 × 10-5 s-1. The optimal superplastic conditions are 940 ° C and 3.3 × 10 -4 s-1, where the average elongation is 2526% and the maximum elongation is 2743% During superplastic deformation, dynamic recovery and recrystallization occurs obviously, and the corporate effect of strain hardening and recrystallization softening decides the superplastic ability directly.