In order to improve the problems of low oxygen supply intensity and long smelting cycle of 210 t large converter in a domestic steel plant， the parameters of the currently used six-hole oxygen lance nozzle were optimized and the jet dynamics characteristics were defined by numerical simulation. The results showed that： When the lance position was less than 1.5 m， the change of axial velocity did not change significantly with the Angle. When the lance position was more than 1.5 m， the decrease of axial velocity increased with the increase of the nozzle Angle. The coalescence behavior of jet was obviously improved with the increase of dip Angle. The effective kinetic energy of the jet decreased rapidly with the flow of the jet， when the lance position was 1.5 m， it only accounted for about 20% of the initial kinetic energy， and then the kinetic energy attenuation slowed down， and the kinetic energy loss was only about 5% when it reached 2.7 m. The optimized design parameters of the six-hole oxygen lance of 210 t converter are as follows： inclination Angle 15.5°， Mach number 2.06， throat diameter 45.89 mm， outlet diameter 61.14 mm. The industrial test results show that the optimized oxygen lance can reduce the oxygen blowing time by 43 s and increase the dephosphorization rate by 11.4%.