The dwell and normal cyclic fatigue behaviors of Ti-5.7Al-3.7Sn-3.5Zr-0.4Mo-0.4Si-0.4Nb-1.0Ta-0.05C (Ti60) forging with a bimodal microstructure at different volume fraction of primary phase (V p ) were investigated. Lower fatigue life was found under dwell fatigue condition than under normal cyclic condition regardless of the value of V p . However, dwell fatigue sensitivity tends to decrease with the decrease of V p . Interior crack initiation characterized by higher facet density was found for dwell fatigued specimens as compared to normal cyclic fatigued ones with fatigue cracks nucleating at the surface or subsurface. Fracture surface analysis based on 3D Measuring Laser Microscope indicates that cleavage occurred favorably at grains to form facets with their normal line at an angle not larger than 15° to the loading axis under dwell loading, while the angle is only less than 5° under normal cyclic loading. It was concluded that more grains involved in dwell fatigue damage which leads to lower fatigue life and higher dwell sensitivity with increase of V p and decrease of V p is helpful to alleviate this effect.