The circulating air system can make full use of the re-transportation capacity of the air and reduce the total real-time emissions, which has become an important choice for industrial ventilation due to its energy-saving and emission reduction characteristics. However, there is a phenomenon of pollutant accumulation in the controlled environment of the circulating air system, and the research on the precise control of the accumulation of pollutants in the controlled environment and the proportion of circulating air is not perfect. In this study, a real-time calculation method for controlling pollutant accumulation in the environment by circulating air system was developed. Based on the intermittency of pollutant emission in the foundry industry, a method for calculating the proportion of circulating air under different process conditions was proposed, and the proportion range of circulating air was dynamically adjusted. The spatiotemporal distribution of pollutants in a controlled environment was studied by CFD discrete phase model (DPM). The results show that the average error between the simulation results and the theoretical calculated values at different times is within 15%, which is in good agreement. The circulating air system can effectively reduce the fresh air volume and the total real-time emission of the dust removal system; The upper limit of the concentration of pollutants in the environment controlled by the circulating air system is determined by the calculation of the intensity of the pollution source, the proportion of circulating air, and the filtration efficiency of the dust collector. In addition, through the dynamic characteristics of pollutant concentration changes under different circulating air ratios in the controlled environment, it is very important to select the appropriate circulating air ratio, which is very important to reduce the pollutant accumulation in the environment controlled by the circulating air system on the basis of energy saving.