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Fe-Mg partitioning between perovskite and ferropericlase in the MgO-FeO-SiO₂ system has been studied up to about 100 GPa at around 2000 K using a laser-heated diamond anvil cell (LHDAC). The compositions of both phases were determined by using analytical transmission electron microscopy (ATEM) on the recovered samples. Present results reveal that the Fe-Mg apparent partition coefficient between perovskite and ferropericlase [K_D^Pv/Fp = (X_Fe^PvX_Mg^Fp)/(X_Mg^PvX_Fe^Fp)] decreases with increasing pressure for a constant FeO of the system, and it decreases with increasing FeO content of ferropericlase. The gradual decrease of K_D^Pv/Fp with increasing pressure is consistent with the spin transition in ferropericlase occurring in the broad pressure range from 50 to 100 GPa at around 2000 K.