The solubility of oxygen in water, fermentation medium, starch solution, yeast extract and Na₂SO₄0, solution was measured under 120 atm and at the temperature between 30 and 50℃ using oxygen-nitrogen mixed gases with different amounts of oxygen at each experiment. In chemical systems, the data on oxygen solubility and used to evaluate the mass transfer in the pressurized fermentor; in biological systems, they are used to increase the productivity of substances such as Polysaccharide, Xanthan gum, Penicillin, Polyhydroxybutyrate(PHB), etc. Four major factors affect the solubility of oxygenpressure, temperature, gas composition and liquid composition The oxygen solubility increased with higher pressure and lower temperature. This study also found out that the solubility is affected by what consists of gases and liquids in the high pressure fermentor.