Under replacement ventilation conditions, a simplified physical model of a tall space (livestock house) was established using ProSim software, and the relevant boundary conditions were set. The airflow size and direction distribution under different air supply and exhaust airflow conditions were obtained by slicing, and the simulation results showed that appropriately increasing the air supply and exhaust airflow helps to increase the pollutant emission rate so that pollutants can be discharged in time, but when the air supply and exhaust airflow were increased to a certain extent, these will cause the airflow vortex phenomenon near the pollutant source, which will enhance the mixing effect of pollutants and surrounding air, making up the pollutant concentration also. The study found that when the indoor air supply and exhaust air volume is increased by 45 times/h, the replacement ventilation effect is optimal and the indoor pollutant concentration is the lowest.