On the basis of previous work, the home-made deformation-testing system was further applied to detect the thickness change of porous nickel materials in the various experimental condition of molten carbonate. The deformation and dissolution behavior of porous nickel and the loading effect on the behavior were in situ studied in the process of oxidation and lithiation. The results indicated that both an obvious deformation and a severe nickel dissolution occurred during the oxidation/lithiation of porous nickel in molten carbonate under loading conditions. Furthermore, the dissolution of nickel from porous nickel was still significant even if without loading. It was found that the deformation of porous nickel closely corresponded to its dissolution during the oxidation/lithiation of porous nickel in molten carbonate.