A system for preventing freezing of a fuel cell comprises: a stack unit for generating an electrical energy and a heat energy; a temperature sensing unit installed at the stack unit; a heater unit operated according to a value sensed by the temperature sensing unit; and a control unit electrically connected to the temperature sensing unit and the extinguishing unit. it is possible to avoid the main parts of the fuel cell from being frozen due to an external temperature change, so that the performance of the entire system can be prevented from deterioration or malfunctioning, thereby increasing the stability of the fuel cell.