The invention discloses an electrothermal conversion control energy-saving heat supply device and an energy saving method thereof. The device comprises an energy storage control system, an electrothermal film heating system and a heating control system. The energy storage control system converts solar energy into thermal energy through the photovoltaic conversion effect and completes charging of astorage battery and storage of heating waste heat energy. Under the control of the heating control system, the electrothermal film heating system adjusts the transfer function of heating to optimizethe maximum utilization rate and stably heats the house through the sandwich electrothermal film. The use of the solar energy is additionally arranged on the basis of the original heating device, andhe waste heat storage and battery charging and discharging process required in the heating process can be effectively processed so that the use efficiency of the heating device can be enhanced, the maximum energy utilization can be completed and the economic benefit and the energy saving effect of the heating device can be improved.