Abstract: A QSTE500TM steel part was bent and cracked during stamping.Macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscopy and energy spectrum analysis were used to analyze the cracking causes of the part. The results show that the high content of sulfur and manganese in the part and the segregation of manganese were the main reasons for the banded structure in the steel. Non-metallic inclusions were distributed in the banded structure, and the interface adhesion between inclusions and matrix was weak, which made the part crack during deformation. The manganese sulfide in the sample caused multiple small crack sources to form in the part, and caused bending cracking of the part during stamping deformation.