Gas hydrate studies are attracting attention of many researchers as an innovative, economic and environmentally friendly technology when it is applied to CO2 capture, transport, and storage. In this study, we investigated whether CO2 hydrate shows the self-preservation effect or not, that is the key property for developing a novel CO2 transport/storage method. Especially the degree of self-preservation effect for CO2 hydrate was studied according to the particle size of CO2 hydrate samples. We prepared three kinds of CO2 hydrate samples varying their particle diameter as millimeter, micron and nano size and measured their change of weight at -15~-30 ℃ under atmospheric pressure during 3 weeks. According to our experimental result, the lower temperature, larger particle size, and compact structure for higher density are the better conditions for obtaining self-preservation effect.