Ni-NiO-NiFe2O4 cermets with different NiO and Ni contents were prepared and their corrosion behaviors in Na3AlF6-Al2O3 melts were investigated in laboratory electrolysis tests. The solubilities of NiO-NiFe2O4 ceramics with different NiO contents were also determined by an equilibration technique. The electrolysis tests showed that excess NiO was beneficial to the reduction of Fe while had little effect on that of Ni in the bath; the steady-state concentrations of Ni, Fe were below the solubilities of corresponding NiO-NiFe2O4 ceramic matrix. The increase of Ni content in cermets had little influence on the steady-state concentrations of both Ni and Fe, which were also far below their solubilities. Post-electrolysis micro examination of anodes showed that Ni metal may be oxidized first and then transferred to the melts by chemical dissolution. Moreover, the impurity ions transferred directionally and gathered near cathode, forming a concentration gradient; such a gradient was affected by a variety of factors and requires further researches.