To eliminate the adverse effect of incompletely mineralized magnesium additive on pellets strength, clarify the interaction between additives and iron ore during the induration process, two types of interaction couples were prepared and scanning electron microscopy-Energy dispersive spectrometer was used to study the diffusion of elements and phase transformation during the induration. Results show that the diffusion of Mg dominates both interactions. The diffusion of Fe from ore to magnesia fines and magnesium olivine are accompanied by the migration of Si, the former generates Magnesioferrite and Forsterite while the latter also generates Fayalite. For the diffusion of Mg from magnesia fines to ore, Mg only reacts with iron oxides and forms Magnesioferrite, but in the ore-olivine couple, Mg both diffuses into iron oxides and silicate, which indicates that the reaction mechanism of two couples is different. The interaction schematic diagrams of each couple are given in this paper. (C) 2019 Elsevier B.V. All rights reserved.