The invention relates to a device and method for removing ammonia from boiler fly ash. The device comprises an ammonia-containing fly ash storage tank, a stirrer, an alkaline additive storage tank, aspray liquid storage tank, an evaporator, a first gas-solid separator, a second gas-solid separator, an ammonia storage tank and a fly ash storage tank. The method comprises the steps: ammonia-containing fly ash, an alkaline additive and water are mixed and stirred, wherein the mass of the alkaline additive and the mass of the water account for 1-2% of the mass of the ammonia-containing fly ash, after stirring, an ammonia initial extraction object and a fly ash initial extraction object are obtained, ammonia and part of fly ash in the ammonia initial extraction object are separated, and thus the ammonia is obtained; and water in the fly ash initial extraction object is evaporated to dryness, then fly ash and air in the fly ash initial extraction object are separated, and thus fly ash is obtained. The ammonia and the fly ash in the boiler fly ash are separated, thus the fly ash meeting the industrial application requirements can be obtained, the separated ammonia is recycled to be secondarily utilized, energy saving and environmental protection are achieved, the structure is simple, the cost is low, using and maintenance are convenient, and wide practicality is achieved.