Abstract: Welding residual stress (WRS) is the dominant factor for the initiation of cracks at the stress concentration point of the weld, which gradually relaxes under the repeated action of vehicle loads. In order to investigate the effect of WRS on the fatigue performance of welds in orthotropic steel bridge decks (OSD), the dynamic evolution law of crack tip stress intensity factor (SIF) under the combined actions of WRS and vehicle load was simulated using finite element method. A fatigue crack propagation simulation process for OSD welds considering WRS was proposed, and the influence of WRS on crack propagation rate and fatigue life was revealed using fracture mechanics theory. The results show that the position of vehicle load has a significant impact on the stress of the weld root and weld toe, with the maximum SIF at the weld toe increased by about 14.3% compared with the weld root. During the process of crack propagation, the ΔK_app at the crack tip gradually increases and is significantly higher than that without considering WRS; However, ΔK_res is affected by residual stress relaxation, and its value shows a periodic decrease. The ΔK_res value is significantly greater than ΔK_app in the initial stage of propagation, indicating that WRS is the main driving force for the propagation of initial cracks. WRS results in a slower propagation rate in the depth direction than in the surface direction, leading to a gradual evolution of fatigue crack morphology towards a flattened shape. Additionally, during fatigue fracture, the deck plate surface is prone to the formation of longer strip-shaped cracks; WRS can accelerate crack propagation, leading to a significant reduction in the fatigue life of OSD.