The authors thought that Trimethylolethane (TME) hydrate had a great potential as a brand-new phase change material (PCM) due to organic hydrate, which was no flammable and no corrosive against metals. The present paper investigates the physical properties, phase separation and corrosiveness against metal about TME hydrate. The phase separation phenomena of TME hydrate in the stagnant melt was investigated on condition that the hydrate was used with a capsule type heat storage system. Furthermore, the corrosiveness of TME hydrate against metals had evaluated to ascertain the possibility of being used as a metal heat exchanger.It was confirmed that the melting point of TME hydrate is 302.8 K and heat of fusion is 218 kJ/kg. Moreover, basic physical properties were measured, such as specific heat capacity, thermal conductivity and density. It was found that TME hydrate can be used as a heat storage material without thickening agent under some concentration. The concentration of TME that occurs phase separation changes according to the melting temperature and retention time in a general system condition. Also, it was found that TME hydrate has no corrosiveness against aluminum, copper, carbon steel and stainless steel. It was suggested that metal beat exchangers made of copper and aluminum could be used for TME hydrate.