The invention discloses a full-automatic low-energy-consumption warming system of a greenhouse. The full-automatic low-energy-consumption warming system comprises an electric temperature control circulating water pump, a water conveying pipe, heat radiation sheets and an automatic warming device with a heat preservation function, wherein the automatic warming device is provided with a liquid capacity cavity, a water outlet and a water inlet; the water outlet of the automatic warming device, the electric temperature control circulating water pump, the plurality of heat radiation sheets and the water inlet are connected in sequence by the water conveying pipe to form a heat-transfer cycle loop; heat absorption coatings coat the outer parts of the heat radiation sheets. The starting temperature of repeatedly heating a heat transfer medium is very high through the heat preservation function of the automatic warming device and the heat absorption function of the heat radiation sheets coated with heat absorption materials, so that the energy consumption is extremely saved, the energy efficiency is high and the warming cost is saved. Overall, the full-automatic low-energy-consumption warming system has the advantages of energy conservation, environment friendliness and no pollution, uniformity in warming, low cost and high energy efficiency, full-automatic warming, water conservation, and flexibility and convenience for setting, and can be widely popularized and applied.