In order to study the causes and processes of cracking of cold heading steel, the specimens with cracking produced in a steel mill were sampled and analyzed.Scanning electron microscopy (SEMEDS) with an energy dispersive spectrometer was used to observe the macroscopic morphology and microstructure of the cracked area and characterize the morphology and composition of the inclusions. It was found that part of the Widmanstatten structure was mixed in the matrix, which reduced the plasticity and toughness of the cold heading steel. Transgranular fracture and oxidative decarburization occurred in the cracked zone, and the average thickness of the complete decarburized layer was 28 μm, which indicated that the surface defects existed before rolling, resulting in cracking of the cold heading steel during rolling. The residual aluminummagnesiumcalcium composite inclusions in steel also directly led to surface defects and cracking. At the same time, improvements were proposed to improve the microstructure and reduce inclusions.