Abstract: A new modified technology is put forward in which weld shaping with trailing impact rolling is used(WSTIR).The integrated device of WSTIR has also been designed.Tensile test and fatigue test has been carried out respectively for under-matched equal load-carrying capacity joints after modifying.Tensile test results show that tensile fracture occurs in the base metal near the weld toe and tensile strength reaches the tensile strength of base metal for equal load-carrying capacity joints after WSTIR.Fatigue test results show that the fatigue life of equal load-carrying capacity joints after WSTIR is significantly greater than the original welded joints.The weld toe arc transition can reduce stress concentration, thereby improve fatigue carrying capacity of WSTIR joints.The results of tensile and fatigue test show that the modified flat-reinforcement joints have the same load carrying capcity with base metal.This shaping method with WSTIR will greatly promote the practical application in engineering for the undermatching equal load-carrying capacity joints.