The utility model belongs to the technical field of the chemical industry, the utility model discloses a flue gas relieving haperacidity tail gas absorbs accurate alkali addition device, it is not accurate in order to solve at the sino -Canada alkali of tail gas absorption process, the excessive alkali that adds causes the extravagant problem of alkali lye, the device includes the tower of absorbthe remnant air, the tower of absorb the remnant air's upper portion is equipped with spray set, the lower part is equipped with the liquid chamber, the upper portion in liquid chamber is equipped with the air inlet, even there is circulation drain the lower part, be connected with circulation fluid PH detector on the circulation drain, the lower part in liquid chamber still is connected with thecirculating pump, the export and the spray set of circulating pump are connected, be equipped with discharge liquid PH detector in the export of circulating pump, it has with the alkali pipeline stillto link on the liquid chamber, be equipped with parallelly connected owner with the alkali valve on adding the alkali pipeline, the vice alkali valve that adds, and the owner adds the alkali valve and the vice alkali valve that adds is interlocked with intelligent fuzzy controller respectively. The utility model discloses a to the accurate control of circulation fluid and discharge liquid pH value, prevented the interior sour water neutralization of liquid caustic soda and tower, effectively reduced the waste of liquid caustic soda, reduced and used the alkali cost.