The invention discloses a supersonic wave-ozone-based flue gas desulphurization and denitration device. Air goes through a first valve and then enters a first dryer, the first dryer and a plasma ozone generator are connected by a flowmeter, the plasma ozone generator has two output paths, one path goes through a third valve and then is orderly connected to a second dryer and a first ozone concentration sensor, the other path goes through a second flowmeter and then is orderly connected to a second valve and a flue gas reaction chamber, flue gas is input into the flue gas reaction chamber, an ultrasonic generator is arranged in the flue gas reaction chamber, liquid water orderly goes through a forth valve, a third flowmeter and an ultrasonic oscillator and then is fed into the flue gas reaction chamber, through ultrasonic wave activation action on water and ultrasonic wave mass transfer enhancement effects, when flue gas and ozone go through water mist subjected to ultrasonic treatment and then enter the reaction chamber, gas and water mist in the reaction chamber are subjected to activation under ultrasonic wave action and produce a lot of hydroxyl radicals and other active particles and SO2 and NOX in the flue gas are removed.