The present invention relates to a gas-steam combined cycle centralized heat supply device and a heat supply method. The gas-steam combined cycle centralized heat supply device comprises a gas-steam combined cycle system connected with a thermal station through a heating network return water heating system; the gas-steam combined cycle system comprises a gas turbine connected with a direct contact type flue gas condensation heat exchanger and a steam turbine via a waste heat boiler; the thermal station comprises a hot water type absorption heat pump and a water-water heat exchanger; the heating network return water heating system comprises a steam type absorption heat pump for recovering flue gas waste heat and a steam-water heat exchanger. The present invention can be widely applied to the industry of power plant waste heat recovery.
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