The supercooling characteristics on microencapsulated phase change material (PCM) as a latent heat storage material were investigated experimentally. The capsulated PCMs were n-Dodecane (C12H26, melting point of 259.9K) and n-Tetradecane (C14H30, 278.9K). The sizes of capsule-samples were from 6 to 1000 μ m in average diameters. ln the experiments, the solidification behavior of supercooled PCM inside a microcapsule was observed with the aide of microscope and high-speed video camera and the solidication temperatures of the samples were also measured by using DSC analyser. lt was found that the degree of supercooling for the capsulated PCM increased with decreasing its diameters. The capsules of same size exhibited a relatively broad distribution of the solidification temperatures due to the different nucleation processes and the stochastic features of the nucleation process inside a capsule. The heat transfer inside still suspensions of the capsules during the solidication process were also investigated. The heat transfer characteristics of the suspension of supercooled PCM capsules was compared with that of non-supercooled PCM suspension. The supercooling inside the capsule were canceled with nucleating agents. Different rates of heat transfer were found due to the difference of solidification behaviors.