Abstract: To improve the fatigue performance of welded joints in commercial vehicle axle housings, this study investigates the effect of shot peening process on the residual stress and structural performance of the support welds of S460Q steel axle housing. Methods including vertical bending stiffness tests, fatigue life tests, and X-ray residual stress measurements were employed to compare and analyze the performance of housings under two processes: "Support Welding - Assembly Shot Peening" (Process B) and "Assembly Shot Peening - Support Welding" (Process A). The results indicate that the performance of housings treated with Process B is significantly superior to Process A. The average vertical bending stiffness of Process B samples increased by approximately 3.8% compared to Process A (maximum deformation reduced by 0.04-0.14 mm); all Process B samples exceeded the standard fatigue life of 800, 000 cycles, while only 33% of Process A samples met the standard, with the maximum fatigue life of Process B being nearly three times that of Process A. Residual stress measurements revealed that Process B introduced compressive residual stresses averaging about -150 MPa in the weld surface layer, effectively counteracting welding tensile stresses; whereas Process A welds exhibited high tensile residual stresses up to 300-400 MPa. After bench testing, the compressive residual stresses partially released and shifted towards tensile stresses. The research demonstrates that adopting the "Support Welding - Assembly Shot Peening" sequence and optimizing shot peening parameters can significantly enhance the fatigue life of axle housings, providing a theoretical basis and data support for manufacturing process optimization.