Abstract: A fuel cell power generation system includes a fuel cell subsystem having a plurality of fuel cell stacks connected in parallel to each other, a reformer, an oxidant gas feeder, a fuel gas exhaust conduit, an oxidant gas exhaust conduit, an inverter, shut-off valves, an exhaust fuel gas dilution conduit, and first and second bypass conduits. When a fuel cell stack is in an abnormal state or out of order and issues an abnormality signal, a part of reformed fuel from the reformer is bypassed through the first bypass conduit to the fuel gas exhaust conduit and diluted with an inert gas such as nitrogen gas from the exhaust fuel gas dilution conduit. The diluted gas is fed to the reformer. Also, air from the oxidant gas feeder, e.g., an air blower, is partly bypassed through the second bypass conduit and the oxidant gas exhaust conduit to the reformer.