Abstract: This invention describes a method to promote the decarburization reaction of the molten steel in a vacuum refining furnace by adding manganese ore into the molten steel.The added manganese ore melts and release oxygen into the steel bath with the additional dissolved oxygen content effectively promoting the decarburization reaction of carbon steel, even below the 50 ppm level of ultra-low carbon content. The addition of the manganese ore increases the oxygen content of molten steel and enables the vacuum degassification treatment to have an effect similar to that of gaseous oxygen blowing without the excessive refractory erosion of the vacuum chamber lining. In this manner, baths having relatively high carbon contents and/or low dissolved oxygen contents can be effectively decarburized to ultra low carbon levels. This invention and the addition technique are not limited in application to RH vacuum-degassing equipment.