Abstract: The fracture of the Cr8 steel stamping die occurred in the process of die testing. The fracture samples were examined by metallographic microscope, sem and eds. The collapse fracture of the stamping die was examined,and the sheet-like extrusion deformation was found on the sinking platform, which indicated that the strength of the material was low. The surface of the platform was heavily oxidized, the sample was heated and oil quenched, and the heating process was not vacuum heat treatment. The R angle of the groove is very small, and the stress concentration is very large, so the stress concentration cracking is easy to occur. The tempered sorbite has been formed in most of the Matrix after heat treatment, and the strength of the material is greatly reduced. Many surface cracks were observed on the side fracture surface, which resulted in severe deformation of the sample Matrix. The fracture of the stamping die is mainly caused by the abnormal heat treatment process, the obvious decrease of material strength and the fracture of the die under the external force. The oxidation delamination of the platform is serious, the R angle of the groove is very small, and the stress concentration is very large.