The invention belongs to the technical field of denitration transformation for power plants, and particularly relates to a flue gas denitration transformation method for a coal-fired generating unit.The method comprises the steps that according to the existing arrangement of the tail of a boiler, a SCR reactor is additionally arranged behind a BK shaft at the tail of the boiler, a SCR reactor isadditionally arranged above the inlet flue of an electric dust remover, and the SCR reactors are arranged in the mode of one boiler with two SCR reactors; flue gas is introduced into the SCR reactorsfrom the outlet horizontal flue of a coal economizer, NOx in the flue gas is removed under the combined action of ammonia and catalysts; and the purified flue gas subjected to the above treatment is introduced into an air preheater. According to the method, by adopting the SCR denitration process and transforming corresponding facilities of the boiler, the denitration efficiency is improved, the environment-friendly emission requirements of high standards are met, and the influence of coal burning on the environment is reduced.