The invention relates to a fuel-
cell power generation system, and in particular relates to a high-power 
proton exchange membrane fuel-
cell power generation system in an 
underwater isolated air environment. The fuel-
cell power generation system comprises a 
proton exchange membrane fuel cell module, a 
hydrogen and 
oxygen storage device, a 
direct current (DC) / DC conversion unit, a monitoring unit, a 
heat exchanger, a water tank, a water pump, a valve and a circulating 
water pipe; a hot water circulating 
branch comprises a thermostatic hot water tank, a circulating hot water conveying water pump, a 
proton exchange membrane fuel cell module, a 
hydrogen storage device and a 
heat exchanger; a cold water circulating 
branch comprises a cold water tank, a circulating cold water conveying water pump, a DC / DC conversion unit and an 
oxygen storage device; a hot and cold water balancing 
branch comprises a thermostatic hot water tank, a hot water control valve, a balanced hot water conveying water pump, a cold water tank, a cold water control valve and a balanced cold water conveying water pump; one end of the monitoring unit is connected with the thermostatic hot water tank, and the other end of the monitoring unit is connected with the cold water tank. The fuel-cell power generation 
system has the advantages that the 
system does not depend on outside air, is safe and reliable, the heat exchange process inside the 
system is simple and direct, and the heat 
cycle efficiency is high.