Abstract: In order to study the surface quality of the edge-cracking steel sheet and find out the root causes of defects,microscope,scanning electron microscopy,energy dispersive spectroscopy and other related test equipments were employed.The results showed that there were four fundamental casues of steel edge cracking: inclusions,severe decarburization at the steel edge,uneven cooling along transverse direction and accumulation of blowholes.In response to the above-mentioned causes,improvement measures such as optimization of steelmaking process,continuous casting,heating scheme and transverse cooling process at rolling section were taken to decrease the slab defect rate due to edge cracking from 30% to 5.1%,resulting in reduction of side trimming.The results provide helpful reference to production practice and quality disputes resolution.