The invention discloses a boiler flue gas waste heat recycling system. Flue gas exhausted from a boiler (21) sequentially passes through an air preheater (22), a flue gas cooler (23), a desulfurization system (26) and a flue gas heat exchanger (29) and enters a chimney (27) for being discharged; the flue gas cooled through the flue gas cooler (23) passes through the desulfurization system (26) and then is cooled inside the flue gas heat exchanger (29) to a temperature lower than the water dew point; the water inlet and the water outlet of the flue gas heat exchanger (29) are connected with a refrigerator (30). By reducing the temperature of the flue gas to be lower than the water dew point through the flue gas heat exchanger, the boiler flue gas waste heat recycling system can reduce the flue gas temperature of the boiler to be lower than the water dew point and accordingly greatly reduce the flue gas temperature, and on the basis of recovering the sensible heat of the flue gas, can further recover the latent heat of water steam inside the flue gas, thereby deeply recovering the waste heat of the flue gas, reducing the coil consumption of the boiler and achieving good economic benefits.