A method for calcining active lime by taking tail gas from a sealing type calcium carbide furnace as fuel for a rotary kiln comprises the following steps: dust-containing high-temperature tail gas from the sealing type calcium carbide furnace which also produces CO enters a tail gas cooling system to be cooled and reduced therein after passing through a closed pipeline, and then is purified in a dust remover through a low temperature tail gas dust removing system; the purified tail gas and coke powder or coal dust are sent to a combustor of a rotary kiln calcination system to be taken as fuelfor lime calcination equipment; limestone enters the rotary kiln calcination system after being preheated by kiln tail hot gas in a vertical preheater and realizing predecomposition; after being calcined by tail gas and coke powder, the preheated limestone appears in the rotary kiln calcination system as active lime which after being cooled by a vertical cooler is sent by transportation equipmentto a finished products storage; air involved in the cooling enters the rotary kiln as primary air which is burnt therein, and the involvement of preheated air in the combustion compensates for the problem that tail gas from the sealing type calcium carbide furnace has a low thermal value; flue gas for preheating the limestone can be emitted at a low temperature and without dust after being subjected to dust removal by a bag type dust remover; and active lime produced by using the method is taken as the raw material for manufacturing calcium carbide.