Boiler flue gas waste heat heating system

The utility model discloses a boiler flue gas waste heat heating system. Flue gas which is discharged by a boiler (21) sequentially passes by an air preheater (22), a gas desulfurization system (26) and a first flue gas heat exchanger (29); a cold source inlet and a cold source outlet of the first flue gas heat exchanger (29) are both connected with a heat pump (20); the heat pump (20) is connected with a heating network circulating water system; and the cold water in the heat pump (20) enters the flue gas heat exchanger (29) through the cold source inlet of the first flue gas heat exchanger (29) to be heated, returns to the heat pump (20) through the cold source outlet of the flue gas heat exchanger (29) and heats heating network return water which passes by the heating network circulating water system of the heat pump (20). By utilizing the boiler flue gas waste heat heating system, the temperature of the boiler flue gas can be reduced to be below a water dew point, and the latent heat of water vapor in the flue gas is further recycled for heating on the basis of recycling the sensible heat of the flue gas, so that the coal consumption of the boiler is lowered, and the system has good economic benefit.