In this study the performance of a novel candidate material for the cathode of molten carbonate fuel eels (MCFCs), pre-oxidized nickel-niobium surface alloy, was investigated under various MCFC cathode conditions by the determination of the equilibrium solubility of nickel ions in the carbonate melt. The following conclusions can be drawn: (1) under a cathode atmosphere of p(CO2)/p(O-2) = 0.67/0.33 atm, the equilibrium solubility of nickel ions in (Li-0.62, K-0.38)(2)CO3 melt at 650 degreesC is about 17 x 10(-6) mol fraction for the nickel oxide electrode and 8 x 10(-6) mol fraction for the pre-oxidized nickel-niobium alloy electrode; (2) under the selected MCFC cathode atmospheres with partial pressure of CO2 varying from 0.1 to 0.7 arm the dissolution reaction of NiO can be expressed as follows: NiO(s) + CO2(Q)= Ni2+ (1) + CO32-; and (3) temperature has less influence on the equilibrium solubility of the pre-oxidized nickel-niobium surface alloy electrode than on that of the NiO electrode. As far as the equilibrium solubility of nickel ions in the carbonate melt is concerned, the pre-oxidized nickel-niobium alloy can be considered as a candidate material for the cathode of MCFCs.