A home-made LVDT displacement-measuring system was developed and applied to study the process of deformation on NiO during early stage of molten carbonate fuel cell (MCFC) operation. A series of in situ deformation tests was performed at a normal temperature (923 K) with porous Ni and NiO plaques under the atmospheres and load conditions in the presence of carbonate electrolyte. The results indicated that the most significant deformation took place when Ni plaque underwent both in situ oxidized and lithiated processes under a load condition, in particular, the deformation of Ni plaque occurred more severely at the beginning of processes.