The behaviors of Fe, S, O and SiO2 in the heterogeneous equilibrium system between liquid copper, white metal, silica-saturated iron silicate slag and SO2 gas, were investigated at 1300°C as a function of partial pressure of SO2 (pso2) varying from 0.007 to 0.2 atm. The quenched samples were analysed chemically, and the thermodynamic explanations were given to the results. The obtained results are summarized as follows:(1) In the slag, with increase in pSO2 (which is proportional to pO2), the solubility of SiO2 decreases, while the (FeIII/FeII) ratio increases. Because of thedissolution of copper oxide, the solubility of silica in slag is higher than that in the plain FeO-Fe2O3-SiO2 system. These results are similar to those of previous studies for Cu-slag-O2 system.(2) In the white metal, with increase in pso2, the content of iron decreases, while of oxygen increases. It is reasonably assumed that iron and oxygen behave as Fes and Cu2O respectively. At infinite dilution in the each binary of Cu2 S-FeS and Cu2S-Cu2O, the activity coefficients of FeS and Cu2O are γ°Fes≈0.4 and γ°Cu2O≈1 respectively.Interaction parameter in the ternary Cu2S-FeS-Cu2O system is εCu2OFes≈ε FeS Cu2O≈-27.(3) In the metal, with increase in pso2, the content of S shows rather constant value (-1%) while the contents of iron and oxygen show similar tend encies with those in the white metal but the values are less than one tenth. The reliable data could not be obtained for oxygen probably due to the evolution of SO2 during solidification.