Abstract: The process of Mg-cored wire feeding was investigated. The Mg cored wire with special structure was applied in inclusion modification in steel. The process of feeding the Mg-cored wire is more smoothly than feeding the Mg-wire with old structure in steel treating at 1600℃, the absorption ratio is higher and more stable than that of the old process. After being treated by Mg-cored wire feeding, the Al₂O₃ inclusions with the big size changes to the fine particles of MgO·Al₂O₃ inclusions. At same time, the Al₂O₃·MnS inclusions changes to the Al₂O₃·MgS·MnS inclusions.