Thermodynamic modeling of the yellow phosphorus production is carried out to understand the producing mechanism of the tail gas, to predict its most probable composition, and to realize its deep purification and multipurpose utilization. The model is based on the typical raw materials composition and the common industrial process parameters of the electric furnace method, using FactSage6.1 and its database package. The predicted relative productivity between yellow phosphorus and byproduct is consistent with the reported values. Furthermore, the main composition of the tail gas can be obtained if kinetic inhibition is taken into account. The thus calculated equilibrium amounts of CO, H2S, and HF and the total amount of As are in good agreement with the results measured in the field, whereas those of PH3, COS, and CS2 are higher. This method of modeling can be used in the gaseous pollution prediction of other industrial chemical processes occurring at high temperatures.