Abstract: Based on the experiment measuring principle of ductile fracture toughness,a numerical model method was promoted for statistic distribution of ductile fracture toughness in this paper.Because this method can deal with the effect of random factors on ductile fracture toughness very well and produce the large number sample of J_Ic easily,the more accurate statistic distribution and parameters of ductile fracture toughness can be obtained by the manner.Meanwhile the method also analyzes the sensitivity of sample number.The calculation results of S316L weld metal shows that the numerical model method is sample,effective and applicable.The sensitivity analyses demonstrate that the number of sample affects greatly the accuracy of statistic distribution and parameters of ductile fracture toughness in weld metal.When the sample number of the J_Ic is less,the more error well appear.