The invention provides a reheating type water bath furnace and belongs to the technical field of natural gas preheating for fuel gas power plants. The reheating type water bath furnace comprises a heating coil, a shell, a heat exchange coil, a PLC, a thermometer, a temperature sensor, a temperature control switch and a water pump. The heating coil is fixed to the lower layer in the shell and is provided with a waste heat inlet and a waste heat outlet. The heat exchange coil is fixed to the upper layer in the shell and is provided with a natural gas inlet and a natural gas outlet. The shell is filled with intermediate media and is provided with a water pump connector, an expansion connector, a pollution discharge connector, a thermometer connector, a temperature sensor connector and a temperature control switch connector. The thermometer is inserted into the shell through the thermometer connector and is fixed outside the shell. The temperature sensor is fixed outside the shell through a temperature sensor interface. The temperature control switch is fixed outside the shell through the temperature control switch interface. The PLC automatically controls a liquid level switch and the temperature control switch according to the temperature of the natural gas outlet, the flow of the water pump is then controlled, and the intermediate media are output at the set temperature. The reheating type water bath furnace is simple in structure and low in operation cost.