In the process of converter iron and steel smelting, the post-combustion oxygen lance can be used to achieve high efficiency post-combustion. The structure of oxygen lance nozzle directly affects the jet and secondary combustion behavior. In this paper, the 260 t converter is taken as the research object, and the three-dimensional model is established by using SolidWorks to explore the jet behavior of the secondary oxygen jet hole of the secondary combustion oxygen lance in the smelting process. Based on the analysis of the jet characteristics, the influence of the angle of the secondary oxygen nozzle on the jet behavior of the secondary combustion oxygen lance was discussed. The simulation results show that the angle of the auxiliary oxygen nozzle has an important influence on the offset and suction of the auxiliary oxygen nozzle jet, the jet velocity, the impact force, and the contact area with CO and then directly affects the efficiency of CO secondary combustion. These also provide a theoretical support for that optimization design of the auxiliary oxygen nozzle hole of the secondary combustion oxygen lance.