Abstract: In terms of the influence of stress-triaxiality on stressstrain field near crack tip and the characteristics of stress-strain field of homogenous materials containing defect, the double-parameter J-Q criterion (J:J-integratian, Q:stress trixial factor), which shows the nature of stress-strain field of welded joint, is put forward. Based on the double parameter J-Q criterion, the failure assessment curve of welded joints containing defect is achieved. The effects of different geometrical dimensions and mis-matehed materials on the founded failure assessment curves of welded joints are analyzed by finite element method. The application of the failure assessment curve of welded joints containing defects based on engineering practices is also discussed.