A thermal power plant flue gas purification and surplus-energy utilization device comprises a boiler, a main economizer, a main air preheater, a tail economizer, a turbine, a condenser, a low-pressure heater, a deaerator, a high-pressure heater, a dust remover, a desulfurizing tower, an absorption heat pump, an external air preheater and a blower. An extraction pipeline of the turbine is connected with the high-pressure heater, the deaerator, the low-pressure heater and the absorption heat pump; an exhaust pipeline is connected with the condenser, and the other end of the condenser is connected with the low-pressure heater; the high-pressure heater is connected with the main economizer; one end of the external air preheater is provided with an inlet and an outlet respectively connected with the absorption heat pump while the other end is provided with an air outlet connected with the main air preheater and a air inlet connected with the blower; the tail economizer is provided with an air inlet, an air outlet, a water inlet and a water outlet, the air inlet is connected with the main air preheater, the outlet is connected with the dust remover, the water inlet is connected with the low-pressure heater, and the water outlet is connected with the deaerator or the high-pressure heater. The thermal power plant flue gas purification and surplus-energy utilization device has the advantages of higher directly-saved steam temperature, and heating steam can be outputted.