Under different stress concentration factors K_t and stress ratios R, the high cycle fatigue (HCF) properties and fracture morphologies of Ti–5Al–5Mo–5V–1Cr–1Fe (Ti-55511) forgings and bars in longitudinal orientation were studied at room temperature. The results show that stress ratio R and stress concentration factor K_t are two important factors that affect the fatigue properties. Both the fatigue strength of forgings and bars increases with increasing stress ratio and decreases with increasing stress concentration factor. The fatigue properties of forgings are better than bars, and the fatigue strength of forgings is 1.08~1.57 times greater than that of bars.