The invention relates to a desulfurization and denitration system by an ozone oxidation double-tower ammonia method. The desulfurization and denitration system sequentially comprises a hydrogen peroxide spraying device, a draught fan, an ozone spraying device, a flue gas mixing device, a front adsorption tower, a rear adsorption tower, a cyclone separator, a centrifugal separator and a drier, wherein the hydrogen peroxide spraying device is arranged at an outlet of a boiler coal economizer, the outlet of the boiler coal economizer is connected to the draught fan through an air preheater and a dust remover and is connected to the front adsorption tower; the ozone spraying device is mounted in front of an inlet flue of the front adsorption tower; and the flue gas mixing device is arranged between the ozone spraying device and the inlet flue of the front adsorption tower. The desulfurization and denitration system disclosed by the invention has the beneficial effects that the integration degree of a technology is high, the desulfurization and the denitration are integrated, the double-tower structure are stable in properties, the desulfurization efficiency and the denitration efficiency are high, the source of an adsorption tower machine is reliable, the added value of by-products is high, little secondary pollution exists, and the operation cost is low.