The invention discloses a 
coal-fired power 
plant flue gas heat 
regenerative system and an energy-saving water-saving ultra-clean discharging method. The temperature of the 
flue gas is reduced to about 90-110 DEG.C through a low-temperature 
coal economizer, and the recycled 
flue gas heat heats primary and secondary wind entering a boiler through a steam air heaters, so that the first stage of heat regenerative cycles is achieved. The temperature of the 
flue gas at the outlet of a desulfurization 
tower is reduced to 30-40 DEG.C through a vacuum 
flash evaporation and solidification device and a low-temperature 
heat pump heat exchange device, and a part of 
water vapor of the 
flue gas is condensed and collected, so that water is saved. The low-temperature 
heat pump heat exchange device absorbs the 
latent heat released in 
flue gas sensible heat and condensation processes, and dry as-fired 
coal and air are heated, so that the second stage of heat regenerative cycles is achieved. A 
boiler slag discharge system recycles the 
waste heat of heat 
slag, and the as-fired coal is heated, so that the third stage of heat regenerative cycles is achieved. When the 
waste heat is not used up, the remained 
waste heat can be utilized, so that energy is saved. Low-temperature desulphurization 
slurry led out from the vacuum 
flash evaporation and solidification device is injected into the desulfurization 
tower, so that the desulphurization efficiency is improved, and an ultra-clean discharging objective is achieved.