Abstract: In electric arc furnace (EAF) steelmaking, the FeO content in slag typically ranges from 20% to 30%. However, there is currently a lack of numerical simulation studies addressing the dynamic evolution of slag foaming within this range of FeO content. In this study, a numerical approach combining the Euler–Euler multiphase flow model and the population balance model (PBM) was employed. The foam height and foaming index of a CaO–SiO₂–Al₂O₃–FeO slag system (basicity = 1.25, temperature = 1773 K) were simulated at FeO contents of 3%, 7.5%, and 15% to validate the model with experimental results, achieving an error of less than 1.4%. Subsequently, simulations were conducted to predict the volume fractions of the slag phase, gas phase, and foam phase, as well as the foam height, at FeO contents of 20%, 25%, and 30%. The results revealed that the formation of stable gas channels during bubble ascent progresses. At a constant gas velocity, higher FeO content shortens the time required to form gas channels. During this channel formation process, the foam phase volume fraction is mainly governed by the formation time of the channels. Once the gas channels stabilize, the foam phase volume fraction becomes primarily influenced by the slag’s physicochemical properties. When the FeO content increased from 3% to 30%, the maximum foam phase volume fractions decreased. Correspondingly, the foaming index decreased from 0.64 to 0.47 as FeO content increased from 20% to 30%. Increasing gas velocity significantly enhances foam height and foam volume fraction, and also accelerates the formation of gas channels.