Abstract: Cold upsetting cracking occurred to cold heading steel. Typical defect samples and their cracks were analyzed by metallographic examination, scanning electron microscopy and energy spectrum analysis. The results show that cold upsetting cracking of cold heading steel was mainly because there existed bigger inclusions at surface and subsurface, and surface scratches formed during rolling. According to the analysis results, some improvement measures were put forward to control inclusions during steelmaking and strengthen the guide adjustment during steel rolling. As a result, the quality of cold heading steel was improved, and the qualification rate of cold upsetting increased.