A fatigue test and numerical simulation on corroded high-strength steel wires with multiple corrosion pits were conducted. A new approach combining the eXtended Finite Element Method (XFEM) and the Equivalent Initial Flaw Size (EIFS) was proposed to investigate three-dimensional fatigue crack growth and life prediction. The EIFS values for the steel wires were determined under various stress ranges and corrosion pit conditions. The fatigue crack propagation path, the fatigue life, and the stress variation under different pit types and depths were investigated. The results reveal a significant linear relationship between the maximum principal stress range and the fatigue life in logarithmic coordinates for steel wires with various pit types. Additionally, the EIFS is found to be dependent on the stress range and the pit depth. All the predicted outcomes fall within a range of twice the margin of error. The accuracy of this novel method is further verified by comparing predicted results with the test data. This research contributes to a better understanding of the fatigue performance of corroded high-strength steel wires and can assist in the design and maintenance of notched components.