Abstract: Considering the present results of stress-strain field of homogenous materials containing defects and the influence of stress-triaxiality on stress-strain field near crack tip of welded joint and based on the double-parameter J-Q criterion, the failure assessment curves of welded joints are builded. For the effects of mechanical inhomogeneity of the welded joints, the distributions of the J-integral (J) and stress-triaxiality Q factors (Q) are discussed by using of the finite element method. The engineering treatment method of each parameter of failure assessment curve is realized through curve simulations to engineering practice.