The invention discloses a 
flue gas low-temperature combined desulfurization and denitration technology method mainly including the steps: 
flue gas after dedusting having a purification temperature and 
humidity meeting desulfurization conditions is sent into a desulfurization 
tower to flow through a desulfurization catalyst 
bed, 
sulfur dioxide in the 
flue gas is oxidized into 
sulfur trioxide under the action of a catalyst, and 
sulfur trioxide acts with water in the 
flue gas to generate 
sulfuric acid; the desulfurization catalyst 
bed is regenerated through progressively-decreased 
sulfuric acid concentration gradient washing; the 
flue gas after desulfurization is sent into a denitration conditioning work section, is dehumidified and heated, and is adjusted to meet requirements of a denitration technology; the 
flue gas after dehumidification and heating is sent into a mixing 
tower and is mixed with injected 
ammonia gas, the mixed flue gas mixed with the 
ammonia gas is sent into a denitration 
tower to flow through a denitration catalyst 
bed, and 
NOx, NH3 and O2 in the mixed flue gas are converted into N2 and water under the action of a denitration catalyst. The problems that a conventional 
flue gas desulfurization and denitration technology is narrow in flue gas applicable scope, high in 
heating energy consumption, high in running cost and the like are overcome.