Low-cost titanium alloy Ti8LC was heat treated by duplex annealing. Its tensile properties were tested, and the fatigue crack propagation behavior as well as fatigue fracture mechanism were studied. Results show that the strength of the alloy increases a little but the ductility decreases with the increase of the first annealing temperature. SEM analysis on the fatigue crack propagation was performed, and the analysis results indicate that the fatigue crack propagates in three modes of three regions. The presplitting region was cleavage fracture. In the stationary state growth region, fatigue crack grew ahead in the form of striation mechanism and many second fatigue cracks were observed in the meantime. In the fast-growth region is mainly dimple. The temperature of duplex annealing has little influence on fatigue crack propagation behavior.