Many titanium alloy subcomponents are subjected to fatigue loading in aerospace engineering, resulting in fatigue failure. The fatigue behavior of Ti 2 AlNb alloy subcomponents was investigated based on the Seeger fatigue life theory and the improved Lemaitre damage evolution theory. Firstly, the finite element models of the standard openhole specimen and Y-section subcomponents have been established by ABAQUS. The damage model parameters were determined by fatigue tests, and the reliability of fatigue life simulation results of the Ti 2 AlNb alloy standard open-hole specimen was verified. Meanwhile, the fatigue life of Ti 2 AlNb alloy Y-section subcomponents was predicted. Under the same initial conditions, the average error of fatigue life predicted by two different models was 20.6%. Finally, the effects of loading amplitude, temperature, and Y-interface angle on fatigue properties of Ti 2 AlNb Y-section subcomponents were investigated. These results provide a new idea for evaluating the fatigue life of various Ti 2 AlNb alloy subcomponents.