During the sintering process, the onset of abnormal grain growth is depend on various factors. The abnormal grain growth behavior, however, was focused only the growth stage compared to nucleation stage. Because most of abnormal grain growth occurred to a rapid mode, the observation of abnormal grain growth was impossible. In this study, we intend to in-situ observe the nucleation stage of abnormal grain using porous alumina. As a result, the liquid phase due to unintended impurities plays a main role for the formation of abnormal nuclei by the rearrangement of small grains due to the capillary force.