Thermodynamic modeling of the sulfide dissolution in the Na₂O–Fe_tO–CaO–MgO–MnO–Al₂O₃–SiO₂ multicomponent slags was performed to investigate the desulfurization of hot metal using Na₂O-containing fluxes. The dissolution behavior of sulfur in the melts was modeled using the modified quasi-chemical model in the quadruplet approximation. This model can take into account the short-range ordering and the reciprocal exchange reaction of cations and anions in oxy-sulfide slags. Experimental sulfide capacity data were well predicted from the model with only three model parameters.