The invention discloses a dry-type deep flue gas desulfurization and denitration integrated method taking manganese hydroxide as a circulating work medium. The method comprises the steps of replenishing a reactor, containing the manganese hydroxide, with flue gas; enabling the manganese hydroxide to react with oxygen in the flue gas at the temperature within a temperature range of 160-50 DEG C so as to generate manganese oxide MnOx (x is more than 1 and less than or equal to 2); meanwhile, enabling the manganese hydroxide to absorb SO2 and NOx in the flue gas and immediately react with the SO2 and the NOx to generate manganese sulfate and manganese nitrate; enabling an alkaline substance to react with the manganese sulfate and the manganese nitrate which are dissolved in water so as to prepare manganese hydroxide again for circulating desulfurization and denitration, wherein the by-products such as sulfate and nitrate produced in the regeneration reaction are useful chemical products. The method can be used for completely removing the SO2 in the flue gas only by using alkaline raw materials such as lime having wide sources and low price, and has the NOx removal rate of 90% or above; the by-products of the method are sulfate and nitrate products which are marketable, so that economic benefit is obtained; furthermore, a recycling and economic dry-type desulfurization and denitration process route is added for the clean utilization of fossil fuel and the atmospheric environment protection.