Abstract: Aiming at the characteristics of the 120 t converter and smelting process of a certain plant of Ma’anshan Iron and Steel Co．，Ltd.，the parameters of the original fourhole nozzle of the oxygen lance were optimized．The number of nozzle holes，nozzle angle，operating pressure，throat diameter，outlet diameter and expansion length had all been adjusted appropriately．Mach number of the optimized oxygen lance nozzle had been increased from 1.98% to 2.05%．Combined with the production practice of the plant，it shows that the optimized 5hole nozzle of oxygen lance can increase the oxygen supply intensity of converter，optimize the dynamic reaction conditions in converter，shorten the oxygen blowing time by 128 s，increase the dephosphorization rate by 4.65 %，decrease w(TFe) of final slag from 18.59 % to 15.84 %，and decrease molten hot metal consumption by 22 kg/t，which is not only conducive to improving the scrap steel ratio of converter，but also to improving the metal yield．