Microscopic observations of the liquid CO2-water-CO2-hydrate system were conducted to measure both the interfacial tensions in these phases and the strength of the CO2-hydrate film. Measurements on hanging drops revealed that the interfacial tension between liquid CO2 and water decreased slightly as the temperature was raised from 266.3 to 284.9 K, and that the average of the interfacial tension was about 29 dyn-cm(-1). Contact angles between a water droplet and a teflon plate were measured before and after the thin film of CO2 hydrate was formed on the droplet. Comparisons of these contact angles indicated that the sums of the interfacial tensions between liquid CO2 and CO2-hydrate film and between CO2-hydrate film and water were about 26% less than between liquid CO2 and water. The destructive strength of CO2-hydrate film formed on the pendant drop was examined by using a process for breaking of the film. Measurements indicated that the strength of the CO2-hydrate film depended on the film thickness. The film thickness of CO2 hydrate was then estimated from the film strength.