<p>Deep-sea equipment operates in harsh marine environments for extended periods, where the fatigue crack propagation in welded structures under corrosion significantly affects structural safety and service life. Due to the unique nature of corrosion fatigue damage, the process of pit formation, development, and small crack propagation is transferred to long crack life based on the equivalent initial flaw size (EIFS) theory. This work focuses on 18Ni (250) angled welded steel plates to investigate the full-life corrosion fatigue crack propagation life at the weld. Firstly, six 18Ni (250) angled welded joint specimens were prepared, consisting of four normal specimens and two pre-cracked specimens, and then subjected to corrosion fatigue testing. Secondly, the full fatigue life of the specimens was calculated based on experimental data of pre-cracked specimens through a joint simulation of ABAQUS-FRANC3D. A full-life corrosion fatigue crack propagation rate model based on EIFS was established, resulting in the derivation of a corrosion fatigue life prediction formula. Finally, the predicted results were compared with the experimental results to validate the accuracy of the prediction formula. This study provides a reference for fatigue damage prediction and safety operation assessment of deep-sea welded equipment.</p>