In order to take into account the influence of welding residual stresses on fatigue crack growth, thermo-elastic-plastic finite element models of steel cruciform welded joints were developed by the ABAQUS software. The distribution and magnitude of longitudinal and transverse residual stresses were obtained in consideration of different welding currents and speeds. Uniaxial tensile fatigue tests on cracked cruciform joints strengthened with carbon fiber reinforced polymer were conducted. The coupling actions of residual stresses and fatigue loads were applied to subsequently simulate fatigue crack propagation via using the Extended Finite Element Method. Good agreement between the simulated and theoretical transverse residual stresses at the weld toe along the plate thickness direction verifies the accuracy of numerical results. The welding speed has a greater impact on residual stresses than the welding current. The stiffness ratio of carbon fiber reinforced polymer and steel plate is larger, and a better reinforcement effect will be achieved. Whether specimens repaired or not, it significantly decreases the fatigue life of cracked welded joints in the presence of residual stresses, but the fatigue crack growth trajectory is almost unchanged.