In response to the application requirements of dual-phase high-strength steel FB590 in various structural and safety components，this study investigated the fatigue fracture morphology and failure mechanism of samples subjected to pre-bending deformation and subsequent annealing treatment.The results reveal that the fatigue fracture surfaces of FB590 samples consist of three distinct regions：the fatigue initiation zone，the crack propagation zone，and the final fracture zone，exhibiting typical characteristics of fatigue failure.In the original sheet samples，fatigue cracks predominantly initiate from surface defects or local stress concentration induced internal inclusions，with the instantaneous fracture zone characterized by large dimples，indicating good ductility.After pre-bending deformation，the R20 samples （r=20 mm） exhibit multi-source fatigue fractures，with cracks initiating from inner surface processing defects.Under high stress conditions，fatigue striations appear groove-ridge shaped，while under low stress conditions，they show cleavage-like morphology.The number and size of dimples decrease，reflecting a reduction in ductility.In the R10 samples （r=10 mm），fatigue cracks initiate mainly from inclusions，and the instantaneous fracture zone exhibits a mixed fracture mode with fewer dimples.Following annealing treatment，the R20an samples maintain a multi-source fracture pattern，initiating from surface defects or inclusions.At high stress condition，the fracture mode is predominantly transgranular fracture，while at low stress condition，intergranular fracture is observed.The final fracture zone comprises a small number of dimples and a large number of micro voids.The R10an samples exhibit single-source fatigue fractures，with evident plastic slip traces along grain boundaries in the crack propagation zone.The dominant fracture mode is transgranular fracture，accompanied by a relatively small number of dimples in the final fracture zone.A comprehensive analysis indicates that pre-bending deformation significantly degrades the fatigue performance of FB590 steel.Although annealing treatment partially improves fatigue resistance，its effectiveness in restoring the ductility loss induced by bending deformation is limited.