Abstract: A batch of spring steel wire rod bars broke during the process of coiling. The reasons for the fracture of the wire rod were analyzed using macroscopic observation, chemical composition analysis, scanning electron microscopy analysis, metallographic examination. The results show that during the packaging process, surface defects were generated on the wire rod. During the straightening process of the coil spring, the wire rod was subjected to straightening force, resulting in stress concentration at the defect site and the initiation of microcracks. The cracks continued to propagate, ultimately led to wire rod fracture.