Abstract: To investigate the influence of different ultrasonic impact treatment (UIT) parameters on welding residual stress (WRS) in U-rib double-sided welded joints of orthotropic steel decks (OSDs), a three-dimensional finite element model was established for the welding process and UIT application at double-sided welded connections of U-ribs. The established UIT finite element model and welding simulation method were validated through experimental data. Based on the thermo-elastoplastic finite element method, a numerical simulation of the welding process for the double-sided welded structure was conducted, and WRS was used as the pre-applied stress field for the UIT model. The effects of process parameters such as impact velocity, needle diameter, overlapping distance, and offset on WRS in the double-sided welded details were analyzed. The results indicate that impact velocity and needle diameter are the key parameters for regulating the WRS amplitude in the weld toe zone of double-sided welded joints, while overlapping distance and offset primarily influence the distribution pattern of WRS within the plate. When the impact velocity is 5 m/s, the depth of the impact residual compressive stress layer reaches 1.92 mm. When the needle diameter increases from 2 mm to 5 mm, the maximum residual compressive stress on the specimen surface increases by 112%. With the increase of overlapping distance, the impact residual compressive stress area along the plate thickness direction at the weld toe exhibits an asymmetric offset feature, and its influence area reaches 36%–48% of the plate thickness. When the offset decreases from 1.5 mm to 0.1 mm, the accumulated plastic strain on the material surface layer increases by approximately 23% compared with the 1.5 mm condition, and the distribution of impact residual compressive stress becomes more uniform.