<p>Crack initiation process could account for the main proportion of fatigue life. In this study, high cycle fatigue behavior of Ti6Al4V ELI alloy with bimodal microstructure was studied and its correlation with crack initiation was investigated. The results show that fatigue crack mainly initiated at subsurface or interior of the tested specimens. Fatigue life generally increases with increasing crack initiation site-specimen surface distance under same/similar stress level. The maximum stress level shows big influence on the locations of crack initiation sites. Higher maximum stress could lead the crack initiation site to an inner position within fatigue specimen, which can be attributed to the strengthening of necking effect. Based on analyses, the influence of maximum stress on the probability of different crack initiation modes was summarized. By comparing the calculation results, the fatigue specimens with interior crack initiation mode have obviously higher threshold stress intensity factor range than other modes, which indicates higher resistance to fatigue crack propagation. Besides, it was found that the fracture surface morphology of fatigue specimens contains three features, including initiation facet, propagation facet, and rough surface with tear ridges. Initiation facets occur most possibly due to the fracture of α_p grain and are always along (0001) plane as well as the biggest shear stress plane.</p> Graphical Abstract <p></p>