Taking an oxygen-rich side-blown lead melting furnace made by a company as the research object, the three-dimensional design software Solidworks was used to construct a model at an equal scale, and established a physical model which is in line with the actual system. Based on the determination of the physical properties of the slag phase and metal phase in the furnace, the VOF multiphase flow model and standard turbulence model in FLUENT were used to simulate the gas–liquid multiphase flow. By adjusting the different inclination angles of the spray gun, we analyzed the distribution changes of key indicators, such as the flow field, average turbulent kinetic energy and gas content in the furnace. At the same time, it was found that the turbulent kinetic energy in the middle of the furnace was large, which could strengthen the winding effect of the material and the best arrangement. The gas content of the upper part of the oxygen gun was high, and the gas content in the middle of the furnace was higher than that in the wall area on both sides and showed a gradual downward trend. If the inclination angle of the spray gun is too small, the agitation of the lower melting area is not strong enough, On the contrary, if the inclination angle is too large, the local flow rate of the sedimentation area increases and the gas content is low. The optimal tilt angle of the spray gun is between 10° and 15°.