Abstract: There exist an equivalent yielding stress and equivalent strain hardening exponent in the viciaity of the crack tip of the heterogeneous crack body, which keeps the assessment expression of fracture mechanics parameters of weldment similar to that of the homogeneous material.In this paper, the effects of the width of weldment, matching properties of weldment, stress condition and mechanical properties of base metal and weld metal on the equivalent fracture mechanics parameters are investigated in detail. The conclusions showed that the width of weldment, matching properties of weldment have strong effects on the equivalent parameters, the stress condition has a little effect on the equivalent parameters and there is no relation between the two equivalent parameters.