Ferromanganese alloy is produced by the carbothermal reduction of MnO2 and Mn2O3 ores at high temperature using a submerged arc furnace (SAF). The production rate and chemical composition of liquid ferromanganese alloy in the SAF process are highly dependent on slag flux composition, coke amount, and temperature controlled by electric power. In the present study, the thermodynamic analysis of high carbon ferromanganese alloy production in SAF has been carried out using the FactSage thermodynamic databases. The slag fluxing strategy to improve Mn yield in the SAF process was studied. In addition, a simple SAF process simulation model was developed to evaluate the energy balance and pre-reduction efficiency of ore in the SAF process.