Sequestration of liquid CO2 in intermediate depth ocean has been considered as a means to reduce atmospheric concentration of the greenhouse gas and to mitigate global warming. The dissolution behavior of CO2 in pure/sea water was investigated under the conditions of the intermediate depth ocean, i.e., high pressure and low temperature conditions. In these conditions, CO2 clathrate hydrate film was formed at the interface between CO2 and water. The solubility of CO2 was derived by measuring the shrinking rates of the diameter of CO2 droplet. The solubility was investigated qualitatively with changing pressure, salinity and temperature. It was clarified that the solubility increased with the increase of pressure and salinity. The hydrate film, which was formed at low temperature condition, much affected the solubility. The authors applied a laser induced fluorescence (LIF) technique for the measurement of pH distribution around a CO2 droplet dissolving into pure water with or without the hydrate film. CO2 solution emitted intense fluorescence dependently on its pH. The visualized images of pH distribution, CO2 concentration around the dissolving CO2 droplet was calculated.