Abstract: The strain-stress distribution rules of welded joint containing a crack on fusion line was analyzed with finite element method. And furthermore, two kinds of welded joints, one with a crack in the middle of the seam and another on the fusion line, were compared. The result showed that the crack structure of the former was the mode of pureⅠ, but the latter was the mode of mixedⅠ+Ⅱ. Considering the expansion of crack-tip-displacement-field, the fracture parameter COD which was defined as the situation of fusion-line containing crack, was studied carefully. And more, the first principal shear angles and the rates of two modes of mixedⅠ+Ⅱwere given out. In the end, the influence of these factors and the complexes on the first principal shear angles of welded joint with a crack on fusion line, were analyzed also.