Abstract: The causes of ER70S-6 welding wire steel drawing fracture were analyzed by chemical composition analysis, mechanical property test, metallographic examination, hardness test, scanning electron microscope and energy spectrum analysis. The results show that the main reason for the “pen-point” fracture of ER70S-6 welding wire steel during drawing were the abnormal undeformed bainite structure and the existence of large-size non-metallic inclusions in the raw material. The reason for the “splitting” fracture was that there were knock defects on the surface.