The pressurized batch fermentor represents an increasing oxygen mass transfer. This method is particularly effective to the cell culture when stirring or vigorous aeration caused the problems such as foaming of the growth medium and increasing cell death rate due to damaged cells. Experiments were conducted in an ideal fermentor by sparging mixed gas into a sulfite solution. The volumetric oxygen mass transfer coefficient in the 0.4∼0.8M solution of sodium sulfite was measured in a 3.8liter agitated and pressurized bioreactor with various working solutions in the presence of CoSO₄ catalyst. The concentrations of the cobalt sulfate catalyst were 1.0×10^-3M, and oxygen concentrations were also varied as 2, 6.8 and 21%. The oxygen transfer coefficient, kla, was found to increase with mixing speed, pressure and temperature.