Abstract: An elastic-plastic finite element method and a virtual crack extension method have been utilized to simulate the J-integral in center-cracked panel (CCP) specimens and three-point bend (TPB) specimens by using MARC finite element program. The path independence of J-integral of welded joint has been investigated. The analysis is done on center-cracked panel specimens and three-point bend specimens with different crack length. strength matching and weld width. The effects of mechanical heterogeneity on plastic zones of welded joint have been investigated. The results show that for shallow crack, the plastic zone turns large in loading process, and the fracture toughness turns high. The plastic zone is more likely to occur with overmatched joint than with undermatched joint. and overmatched joint is more inclined to show the fracture behavior of shallow crack than undermatched joint Therefore, the fracture-resistant capability of overmatched weld is better than that of undermatched weld. The strength matching factor M is an important factor affecting the J-integral. The J-integral value is variable with the diversity of weld width.