The invention discloses a boiler-turbine coupled flue gas waste heat utilization system capable of preheating air based on condensed water, which belongs to the field of energy conservation of electric stations. The boiler-turbine coupled flue gas waste heat utilization system mainly comprises a main economizer, a main flue, a bypass flue, a confluence flue, a main air preheater, smoke water heat exchangers, a high-pressure heater, a low-pressure heater, a deaerator, a flue gas-air heater and a condensed water-air heater. Cold air is preheated by extracting low-temperature condensed water in some of thermodynamic systems and low-temperature flue gas of a boiler through utilizing the condensed water-air heater; a primary smoke water heat exchanger and a secondary smoke water heat exchanger are used for heating the feeding water and the condensed water so as to replace extraction steam, with higher pressure, of a steam turbine. According to the flue gas waste heat utilization system, waste heat is effectively utilized, and the air is preheated by utilizing the low-level condensed water and the low-temperature flue gas of the boiler, so that the high-pressure extraction steam used for heat return is saved, thus work of a machine set is remarkably increased, and deep energy conservation and consumption reduction of a coal-fired generator set can be realized; furthermore, a problem of low-temperature corrosion of a waste heat utilization heating surface is relieved, and remarkable economic benefit is obtained.