From a thermodynamic perspective, the present study has been performed to investigate the effect of SiO₂ level in agglomerated fluxes on the element transfer behavior of essential elements, by applying CaF₂-Na₂O-SiO₂ agglomerated fluxes with varying SiO₂ contents. Element transfer behavior is quantified by the Δ value. The impact of SiO₂ and heat input upon element transfer behavior is interpreted. Additionally, a possible thermodynamic approach to predict high basicity flux O potential and weld metal composition is proposed and evaluated. It is revealed that the consideration of the gas-slag-metal equilibrium is able to place constraints on the transfer behaviors (of O, Si, and Mn) and formation of gases. In submerged arc welding metallurgy, the empirically determined basicity index models proposed by Tuliani have been applied for more than 50 years to predict flux O potential and weld metal oxygen content. However, it is well known by welding practitioners that the flux basicity index model can only predict the changing trend of flux O potential when the flux basicity index is lower than 2.0. The present study has proposed a new thermodynamic method to identify the flux O potential for fluxes with a basicity index higher than 2.0. Additionally, the experimental evidence for the Mitra kinetic model has been provided.