A structure-based modeling of the CaO-'FeO'-MgO-Al2O3-SiO2 system and its subsystems was investigated based on iron extraction from nickel slag by aluminum dross. Parameters optimization in the present model indicated that the coefficient of free O2-in FeO, aO2F-eO , on the lengths of network linkage had the largest value and O2F-eO (free O2-in FeO) had the largest mobility. The coefficients of bridging oxygen (aSi-O-Al and aAl-O-Al) were lower than those of non-bridging oxygen and free oxygen (O2-). Viscosity prediction for the CaO-'FeO'-(8 wt.％) MgO-Al2O3-SiO2 system was conducted at a fixed slag basicity, which indicated that the predicted viscosity changed monotonously with the FeO content. However, the non-monotonous evolution with Al2O3 content reflected the amphoteric behavior of Al2O3. In addition, the performances of the present model in predicting viscosity from binary ('FeO'-SiO2) to quinary (CaO-'FeO'-MgO-Al2O3-SiO2) system were analyzed and a comparison with the established models was made.