Abstract: The nodular cast iron samples with and without defects were fabricated. Using the industrial CT tomography method, the samples with defects were scanned to analyze the spatial distribution information and morphological characteristics of the defects, and the samples with defects were stripped layer by layer by using the milling machine,photographed and recorded. The obtained layer-by-layer defect photos were compared and analyzed with the corresponding CT scans, and the results verify the effectiveness of CT scanning technology. At the same time, the tensile test results of ductile iron samples with defects and without defects shows that shrinkage porosity seriously affects the mechanical properties of nodular cast iron, reduces its elastic modulus and strength limit, especially the material elongation, and makes it easy fail and fracture at the defects.