The invention relates to a method and 
system for comprehensive utilization of 
tail heat of a boiler. According to the method and 
system for comprehensive utilization of the 
tail heat of the boiler, low-level steam extraction is carried out by means of a 
turbine, in-boiler 
cold air in a boiler air inlet duct connected with the boiler is heated by extracted steam through a steam 
air heater, heated 
cold air in the steam 
air heater enters an air pre-heater through the boiler air inlet duct, heat exchange is carried out in the air pre-heater between part of 
smoke from a boiler 
economizer or a denitration device and the heated 
cold air, and the other part of 
smoke is used for heat exchange of part of supplied water through a 
water supply economizer. According to the method and 
system for comprehensive utilization of the 
tail heat of the boiler, the low-pressure steam is extracted to heat the cold air so that the heat of the steam is recovered to reduce cold source loss, part of the high-temperature 
smoke is saved at the same time, and the saved high-temperature smoke is used for heating part of the supplied water through an outlet 
flue of the 
economizer or an outlet 
flue the denitration device; high-level extraction steam of the 
turbine is saved due to the fact that the high-level smoke is used for heating part of the supplied water, the saved high-level extraction steam can continue to work in the 
turbine, and then the efficiency of the turbine is improved and fuel 
coal is saved.