Abstract: Pointing at the cracking problem of 45 round steel in cold drawing processing, the analysis was carried out from the aspects of material composition, microstructure, inclusions, dimensional accuracy and so on.The results showed that the larger side of round steel bore the large tensile stress in the process of drawing, as a result of the larger ovality of round steel.When the stress exceeded the tensile strength of steel surface, a transverse crack emerged in the surface of round steel, and expanded in further processing.