Abstract: In order to accurately predict the fatigue life of materials and improve the accuracy of structural fatigue life prediction, the method of ABAQUS finite element numerical simulation to predict the fatigue life of specimens was studied. Based on Tanaka-Mura dislocation theory, ABAQUS was redeveloped by using Python language. The fatigue crack initiation life of S960QL martensitic steel and Ti₂AlNb titanium alloy joint was simulated and predicted. The representative volume element is generated by Tyson polygon method, and the micro sub-model is established. Two perpendicular slip bands of bcc structure are considered as potential crack initiation locations, and several parallel slip bands with the same orientation are simulated. The crack initiation life at the critical point from the crack initiation stage to the crack growth stage is given by the calculated crack growth rate change. The simulation results show that the crack initiation life is in good agreement with the experimental data except the columnar crystal structure.