Disclosed is a power control system and method of a fuel cell including a fuel cell that generates electricity; a load device that is electrically connected to the fuel cell; a DC/DC converter that is disposed between the fuel cell and the load device, and converts power between a low side of the DC/DC converter electrically connected to the fuel cell and a high side of the DC/DC converter electrically connected to the load device; a battery that is electrically connected to the high side of the DC/DC converter in parallel with the load device; and a controller that monitors a voltage of the high side of the DC/DC converter or a voltage of the low side of the DC/DC converter, and controls output power of the fuel cell or power consumption of the load device based on the monitored voltage of the high side or the monitored voltage of the low side.