Abstract: The crack and break phenomenon occurred on the cold drawing wire process of φ6.5mm LS steel wire coil to φ3.2mm cold drawing wire. The defects were analyzed. The reasons are that the speed of controlling cooling is too fast when high-line rolling; during the refining of steel-making ladle, the scum is not removed, the P and S is not removed to the lower limit, and the continuous casting billet has internal segregation and microcracks. According to the causes of defects, the P and S should be strictly removed to the lower limit in molten steel refining, and the cooling rate after high wire finishing rolling should be reasonably controlled.