Abstract: In order to quantify the service life of a certain type of mechanical TB8 titanium alloy bolt, the typical bolt sample was taken as the target object, and the metallographic microstructure, surface hardness distribution, residual stress, fatigue life and fracture morphology of TB8 titanium alloy bolt were analyzed. The results show that the average fatigue life of TB8 titanium alloy bolt sample at 20, 0, −20 and −40 ℃ is 2.46×10⁵, 2.83×10⁵, 2.96×10⁵ and 3.74×10⁵ cycles number, respectively. Based on the bolt fracture morphology, the fatigue fracture failure mechanism and mode at different temperatures are revealed. The fatigue failure mode changes from plastic fracture at normal temperature of 20 ℃ to cleavage fracture and brittle fracture with the decrease of temperature.