Abstract: A three dimensional transient mathematical model for the 100 t oxygen top-blown converter has been carried out using the numerical simulation software fluent.The impact depth,impact area and molten bath velocity distribution had been obtained at different oxygen lance height and oxygen lance nozzle angle.It is found out that under the same condition,raising the lance position leads to larger diameter of pit created by jets,while the impact depth decreases.As the nozzle hole cone angle increases,the diameter of pit created by jets become larger,while the impact depth decreases.Low lance position is beneficial to increase flow velocity of the liquid steel at the upper molten bath,while high lance position is conducive to promote the liquid steel flow of the bottom bath.Increasing the nozzle hole cone angle promotes the large high-speed surface zone area,but the low speed zone area at the bottom of the molten bath has been increased as well.