Abstract: Based on this fact that it is difficult to control of the total oxygen less than 10×10^-6 when smelting bearing steel in a 100 t EAF,the inclusions in bearing steel billets were analyzed by full-size three-dimensional analysis and large sample electrolysis in the paper.The result showed that the content of large inclusions is higher,dominant sphericalAl₂O₃ system inclusions and the massive inclusions containing K.The spherical Al₂O₃ system inclusions are mainly derived from deoxidation products and the massive inclusions containing K are mainly come from slag entrapment from the mold.Therefore,the removal effect of Al₂O₃ system inclusions can be improved by optimization of reactor flow and the effect of ladle argon,and the inclusions containing K are reduced by the optimization of mould flow field and the adjustment of electromagnetic stirring.The Al₂O₃ group inclusions are larger.A small amount of Mg or Ca exist in the liquid steel can tranfer,Al₂O₃ group inclusions into the smaller MgO·Al₂O₃、MgO or CaO·Al₂O₃·MgO inclusions.