Abstract: The parameters of the Gurson-Tvergaard-Needleman(GTN) damage model were obtained by using the finite element reverse calibration method. Based on the GTN model, the uniaxial tensile deformation process of QT500 ductile iron with defects was simulated, and the normal distribution function describing the internal shrinkage dispersion of the material was proposed to describe its effect on mechanical properties. The results show that GTN damage model can accurately reflect the damage evolution of ductile iron materials. As the variance of the porosity distribution function increases, the porosity distribution widens, and the bearing capacity of materials decreases.