Abstract: Weld shaping with trailing impact rolling (WSTIR) is a new weld shaping and modifying technique to reduce the residual stress and distortion and improve load-carrying capacity of under-matched joint. Vickers hardness test and residual stress test were carried out for under-matched equal load-carrying joint in as-welded state and after WSTIR,respectively. Hardness test results show that the surface hardness,both on weld beam and weld toe,for equal load-carrying joint after WSTIR was significantly higher than that in as-welded state, which revealed that WSTIR had work-hardening effect on key load-carrying areas for equal load-carrying joint. Residual stress test results show that both longitudinal and transverse residual stresses on under-matched joint after WSTIR were remarkably lower than those in as-welded state. Especially,longitudinal compressive residual stress appeared in the weld beam and weld toe after WSTIR,which can undoubtedly improve the load-carrying capacity for under-matched joint.