Abstract: The fuel cell of 1kW H2-O2 stack for underwater applications has been designed and constructed. Alkaline solution which was separated from the gaseous reactants by double asbestos diaphragm was used in the cell stack as mobile electrolyte. One of the advantages of this stack is that there is no need to control temperature strictly, and the stack can operate at a temperature range from 60 to 100℃. Cascading sequence and double gas compartment used in the gas path design made the stack more reliable. Water and waste heat produced in the stack were removed through the circulation of the electrolytes by using magnetically coupled D. C. pump. The tail gas coming from the stack was introduced into the catalytic reactor where H2 reacts with O2 to form water, which reduced the volume of tail gas storage tank.