At the Egyptian Iron and Steel Company, attention is constantly focused on improving basic steel making practice with the aim of improvement of blowing regime and the addition of forming slag materials system. A number of factors considered important in controlling the properties of steel products and affecting the residual manganese in the basic Oxygen furnace (BOF) have been investigated by changing some industrial parameters, aiming at optimizing the residual manganese in BOF. The studied factors were manganese oxide in the slag, iron oxide in the slag, tapping temperature, Slag basicity, Lance height, blowing time, and carbon content. It was found that residual manganese increased from 0.25 to 0.35 % wt, due to the reduction of both MnO in slag from 22% to 15% and FeO from 21 to18%, also the increase of tapping temperature from 1650 oC to 1670 oC caused an increase the residual manganese from 0.27% to 0.35%, and the slag basicity decrease from 4.25 to 3.8 led to an increase in the residual manganese from 0.25 to 0.37%. Also, the change of the lance height from 1050 mm to 825 mm caused an increase in the residual manganese from 0.27 % to 0.33 %. These results are believed to be reflected on the total energy consumption and ferromanganese additions needed for producing specific grades.